Air conditioning system and method for constructing the same

ABSTRACT

An air conditioning system includes a compressor unit including a compressor, a heat exchanger unit including an outdoor heat exchanger, an indoor unit, and a valve unit including a liquid control valve and a gas control valve. The heat exchanger unit is installed in a first space, while the compressor unit and the valve unit are installed in a second space. The system further includes a first leakage detector disposed in the second space, and a ventilation control structure that is configured to switch the state of the second space from a first state to a second state when the detected concentration of the first refrigerant is equal to or greater than a first detection value threshold, in the second state a ventilation of the second space being promoted more than in the first state.

TECHNICAL FIELD

The present invention relates to an air conditioning system and a method for constructing the air conditioning system.

BACKGROUND ART

In an air conditioning system for a plurality of target spaces, each of a liquid refrigerant pipe and a gas refrigerant pipe of a heat pump circuit is branched into a plurality of sub piping systems. The branched sub pipes in the sub piping systems are often provided with valves to zone the sub piping systems.

Meanwhile, each valve used in the heat pump system tends to become a leakage point of refrigerant, and thus needs to be regularly checked and repaired as necessary. Hence, for the convenience of monitoring and maintenance, it is common to design a piping of a heat pump system so as to arrange a plurality of valves in one place. For example, EP 3 091 314 A1 proposes to integrate a plurality of valves of the refrigerant sub pipes within a single casing to form a valve unit. Thereby, it is possible to not only ease the burden of monitoring/maintenance but also prevent refrigerant leaked at any valve from spreading to the surrounding area.

However, a heatsource-side unit of the air conditioning system, which includes a compressor and an outdoor heat exchanger, also includes potential leakage points of refrigerant. Hence, the configuration proposed by the EP 3 091 314 A1 is not sufficient to improve safety of an air conditioning system regarding refrigerant leakage.

SUMMARY OF INVENTION

The object of the present invention is to provide an air conditioning system and a method for constructing an air conditioning system that can further improve safety regarding refrigerant leakage.

A first aspect of the present invention provides an air conditioning system comprising: a compressor unit that has a compressor configured to compress first refrigerant; a heat exchanger unit that has an outdoor heat exchanger configured to exchange heat between air and the first refrigerant or between air and heat medium, the heat medium being subjected to a heat exchange with the first refrigerant; at least one indoor unit that has an indoor heat exchanger configured to exchange heat between the first refrigerant and air in a target space to be air-conditioned or between second refrigerant and air in the target space, the second refrigerant being subjected to a heat exchange with the first refrigerant; and at least one valve unit that has at least one liquid refrigerant pipe portion and at least one gas refrigerant pipe portion configured to allow the first refrigerant or the second refrigerant to flow therein between the compressor unit and the indoor unit, at least one liquid control valve disposed in the liquid refrigerant pipe portion, and at least one gas control valve disposed in the gas refrigerant pipe portion, wherein: the heat exchanger unit is installed in a first space; the compressor unit and the valve unit are installed in a second space which is different from any of the target space and the first space; and the air conditioning system further comprises a first leakage detector that is disposed in the second space and configured to detect at least a concentration of the first refrigerant in air, and a ventilation control structure that is configured to switch the state of the second space from a first state to a second state when the detected concentration of the first refrigerant is equal to or greater than a first detection value threshold, in the second state a ventilation of the second space being promoted more than in the first state.

Since the heat exchange unit and the compressor unit are separated into different spaces, it is possible to make their ventilation environments different from each other. The second space being different from any of the target space and the first space means that the state of air in the second space has no direct relationship with the state of air in any of the target space and the first space. The first space may be an outdoor space or a space through which outdoor air is allowed to pass. Thus, the outdoor heat exchanger in the first space can be freely supplied with drafts of outdoor air, while the ventilation state of the second space in which the compressor unit and the valve unit are disposed can be restricted. For instance, the second space can be substantially closed in normal times. Thereby, when a refrigerant leakage has occurred at any of the compressor unit and the valve unit, the second space can prevent or restrain the leaked refrigerant from spreading to the surrounding area. Moreover, concentration of the leaked refrigerant in the second space can be decreased by discharging the air from the second space to an external space of the second space. Furthermore, the second space can be substantially closed during a normal operation of the heat pump system, and a refrigerant leakage detection can be made based on concentration of refrigerant in this substantially closed space.

Thus, it is possible to swiftly detect an occurrence of a refrigerant leakage in any of the compressor unit and the valve unit and promote the ventilation of the second space by the ventilation control structure at an early stage. Thereby, it is possible to prevent concentration of the leaked refrigerant in both the second space and the surrounding area of the second space from becoming high in a more secure manner. This allows the monitoring/maintenance person to safely monitor, maintain, or repair the compressor unit and/or the valve unit. Accordingly, it is possible to improve safety of the air conditioning system regarding refrigerant leakage. It should also be noted that the above effects regarding refrigerant leakage in the compressor unit or the valve unit can be achieved without affecting the ventilation environment of the outdoor heat exchanger.

In addition, the ventilation control structure is used in common for the compressor unit and the valve unit. Hence, the safety of the air conditioning system can be improved while preventing an increase in the installation cost of the system. Accordingly, with the air conditioning system according to the first aspect, it is possible to improve safety regarding refrigerant leakage at low cost, even in a case where the compressor should be arranged inside a building.

Here, the external space to which the air is discharged by the ventilation control structure is preferably not an outer space directly surrounding the second space or an indoor space where a human or animal could come or reside. The external space is preferably an outdoor space.

According to a preferred embodiment of the air conditioning system mentioned above, the ventilation control structure includes a passage control structure that is configured to, when the detected concentration of the first refrigerant is equal to or greater than the first detection value threshold, switch a state of at least one airflow passage between the second space and an outer space outside of the second space from a first passage state to a second passage state, in the second passage state air being allowed to pass through the passage more easily than in the first passage state.

The airflow passage may be an opening formed in a building structure defining the second space therein, a duct penetrating the building structure, a window frame or door frame embedded to the building structure, or the like. The passage control structure may include a check air damper, a shutter, a window plate, a door plate, or the like. The passage control structure may be configured to close the passage to achieve the first passage state in normal times, and open the passage to achieve the second state. Thus, the passage control structure need not necessarily cause a forced ventilation of the second space, but may simply induce a natural ventilation of the second space. Since a device for causing a forced ventilation such as a ventilator is not necessarily required, it is possible to avoid an increase in installation cost of the air conditioning system. It is preferable that two or more airflow passages are formed in the building structure to effectively induce the natural ventilation.

According to another preferred embodiment of the air conditioning system mentioned above, the ventilation control structure includes a discharge structure that is configured to operate to discharge air from the second space when the detected concentration of the first refrigerant is equal to or greater than the first detection value threshold.

With this configuration, since a forced ventilation is caused, it is possible to discharge the air containing refrigerant from the second space in a more secure way.

According to further another preferred embodiment of the air conditioning system mentioned above which has the discharge structure, the discharge structure includes a ventilator that is configured to draw air from the second space towards an external space which is different from any of the target space and the second space, a controller that is configured to control the ventilator to operate when the detected concentration of the first refrigerant is equal to or greater than the first detection value threshold, and a check air damper that is configured to keep closed an airflow passage between the second space and an outer space outside of the second space, and open the airflow passage when the ventilator is in operation.

With the above configuration, it is possible to effectively discharge the air from the second space when a refrigerant leakage has occurred in the second space. Here, the ventilator may be configured to blow air to push the air within the second space out, or suck air to draw the air in the second space out.

According to further another preferred embodiment of any one of the air conditioning system mentioned above which has the ventilator, the controller, and the check air damper, the second space is defined by a building structure; and the ventilator and the check air damper are disposed to the building structure.

With the above configuration, the second space can be obtained by utilizing a building structure of the building to which the air conditioning system is installed, and the ventilator and the check air damper can be arranged by utilizing openings formed in the building structure. The second space may be one of the rooms of the building, or two rooms of the building which are connected to each other to form a single continuous space. Hence, it is possible to easily achieve the ventilation control structure. It is preferable that the building structure is configured such that the second space is substantially isolated from the outer space thereof when the ventilator is not in operation and the check air damper is closed.

According to further another preferred embodiment of any one of the air conditioning systems mentioned above which has the ventilator, the controller, and the check air damper, the air conditioning system further comprises: first and second casings one of which accommodates the compressor unit and another one of which accommodates the valve unit as part of the second space; a connection structure connecting the internal spaces of the first and second casings; an intake duct connecting the outer space of the second space and the internal space of the first casing; and a discharge duct connecting the internal space of the second casing and the external space, wherein the first leakage detector is disposed in the first or second casing that accommodates the compressor, the check air damper is disposed to the intake duct, and the ventilator is disposed to the discharge duct.

With the above configuration, it is possible to make smaller the space in which a refrigerant leakage is to be detected and from which air is to be discharged, even in a case where the compressor unit and the valve unit are distanced from each other. Thus, it is possible to swiftly detect a refrigerant leakage occurred in any of the compressor unit and the valve unit, and thus swiftly discharge air containing leaked refrigerant. Moreover, even in a case where it is difficult to achieve a substantial isolation of the second space, it is possible to perform the swift detection of refrigerant leakage and the swift discharge of air without a large-scale modification of the building structure. Furthermore, the capability of the ventilator can also be made smaller when the space to be ventilated is smaller. Hence, it is also possible to reduce the installation cost of the air conditioning system.

The intake duct and/or the discharge duct shared duct may be extended to the outdoor space. The ventilator may be configured to further discharge air surrounding the first and second casings. The ventilator may be disposed outside the second space.

Here, for each of the compressor unit and the valve unit, the casing and other elements of the unit may be manufactured together. Thereby, it becomes easier to design the unit so as to enhance their performances such as airtightness of its casing. It also becomes easier to optimize the dimension of the unit, and a position of a maintenance door of the casing. Hence, it is possible to improve not only safety but also maintainability and functionality of the air conditioning system. Alternatively, the casing may be a retrofitted casing which is to be assembled around elements of an existing compressor unit or valve unit.

According to further another preferred embodiment of any one of the air conditioning systems mentioned above which has the ventilator, the controller, and the check air damper, the air conditioning system further comprises: first and second casings one of which accommodates the compressor unit and another one of which accommodates the valve unit as part of the second space; a first intake duct connecting the outer space of the second space and the internal space of the first casing; a second intake duct connecting the outer space of the second space and the internal space of the second casing; a connection structure connecting the internal spaces of the first and second casings; a discharge duct connecting the connection structure and the external space, wherein the first leakage detector is disposed in the first or second casing that accommodates the compressor, the check air damper is disposed to each of the first and second intake ducts, and the ventilator is disposed to the discharge duct.

With the above configuration, the internal spaces of the casings are connected to each other in parallel. In other words, each of the internal spaces communicates with the discharge structure without being interposed by any other casing. Hence, it is possible to reduce static pressure capacity required of the ventilator.

According to further another preferred embodiment of any one of the air conditioning systems mentioned above which has the ventilator, the controller, and the check air damper, the air conditioning system further comprises: a casing accommodating the compressor unit and the valve unit as part of the second space; an intake duct connecting the outer space of the second space and the internal space of the casing; a discharge duct connecting the internal space of the casing and the external space, wherein the first leakage detector is disposed in the casing, the check air damper is disposed to the intake duct, and the ventilator is disposed to the discharge duct.

With the above configuration, it is possible to make smaller the space in which a refrigerant leakage is to be detected and from which air is to be discharged. Thus, it is possible to swiftly detect a refrigerant leakage occurred in any of the compressor unit and the valve unit, and swiftly discharge air containing leaked refrigerant. Moreover, even in a case where it is difficult to achieve a substantial isolation of the second space, it is possible to perform the swift detection of refrigerant leakage and the swift discharge of air without a large-scale modification of the building structure. Furthermore, compared with the configuration in which two casings are arranged, the cost for forming the space to be ventilated can be reduced. The capability of the ventilator can also be made smaller when the space to be ventilated is smaller. Hence, it is also possible to reduce the installation cost of the air conditioning system.

According to further another preferred embodiment of any one of the air conditioning systems mentioned above which has the ventilator, the controller, and the check air damper, the indoor heat exchanger is configured to exchange heat between the second refrigerant and air in the target space; the liquid refrigerant pipe portion and the gas refrigerant pipe portion of the valve unit are configured to allow the second refrigerant to flow therein; the air conditioning system further comprises a second leakage detector that is disposed in the second space and configured to detect at least a concentration of the second refrigerant in air; and the controller is further configured to control the ventilator to start operating when the detected concentration of the second refrigerant is equal to or greater than a second detection value threshold.

With the above configuration, in any case of when the detected concentration of the first refrigerant is equal to or greater than a first detection value threshold, and when the detected concentration of the second refrigerant is equal to or greater than a second detection value threshold, the controller is configured to control the ventilator to start operating. Thus, even in a case where the air conditioning system is of a cascade-type which uses different types of refrigerants in the compressor unit and the valve unit, it is possible to improve the safety regarding leakage of any of the refrigerants.

According to further another preferred embodiment of any one of the air conditioning systems mentioned above which has the first and second casings and the second leakage detector, the compressor unit further has a refrigerant heat exchanger configured to exchange heat between the first refrigerant and the second refrigerant; the first leakage detector is disposed in the first casing; and the second leakage detector is disposed in the second casing or a space which is part of the second space and not part of the internal spaces of the first and second casings.

With the above configuration, it is possible to detect a leakage of the second refrigerant from piping outside of the casings. Thus, the safety of the air conditioning system can be further improved.

According to further another preferred embodiment of any one of the air conditioning systems mentioned above, the air conditioning system further comprise: first connection pipes connecting the outdoor heat exchanger unit and the compressor unit such that the first refrigerant or the heat medium circulates therebetween; and second connection pipes connecting the compressor unit, the valve unit, and the indoor unit such that the first refrigerant or the second refrigerant circulates between the compressor unit and the indoor unit via the valve unit.

With the above configuration, a heat pump circuit is formed between the outdoor heat exchanger and the indoor heat exchanger.

According to further another preferred embodiment of any one of the air conditioning systems mentioned above, the air conditioning system comprises a plurality of the indoor units; and the valve unit further has at least one liquid refrigerant branch pipe branching the liquid refrigerant pipe portion towards the indoor units and at least one gas refrigerant branch pipe branching the gas refrigerant pipe portion towards the indoor units.

The branching points of the refrigerant pipes are also potential refrigerant leakage points. Hence, since such potential leakage points are also accommodated in the second space, the safety of the air conditioning system regarding refrigerant leakage can be further improved.

According to further another preferred embodiment of any one of the air conditioning systems mentioned above, the second space is a space which is any one of a machine room, a computer room, and a warehouse in a building.

With the above configuration, the second space is a space where a human is unlikely to reside in normal times. Thus, the safety of the air conditioning system regarding refrigerant leakage can be further improved.

A second aspect of the present invention provides a method for constructing any one of the air conditioning systems mentioned above, comprising: installing the compressor unit and the valve unit in the second space which is defined by a building structure of a building; disposing the first leakage detector in the second space; installing the heat exchanger unit in the first space; installing the indoor unit in a space which is within the building and different from the first space and the second space; connecting the outdoor heat exchanger unit and the compressor unit such that the first refrigerant or the heat medium circulates therebetween; connecting the compressor unit, the valve unit, and the indoor unit such that the second refrigerant circulates between the compressor unit and the indoor unit via the valve unit; and installing the ventilation control structure to the building.

By the above method, it is possible to obtain any one of the air conditioning systems mentioned above, and the building installed with the air conditioning system.

According to a preferred embodiment of the method for constructing the air conditioning system mentioned above, the building structure includes a floor, a ceiling facing the floor, at least one wall which connects the floor and the ceiling and surrounds a space between the floor and a ceiling, and a door arranged in the floor, the ceiling, or the wall.

With the above configuration, a room of the building can be used as the second space. Thus, it is possible to improve safety regarding refrigerant leakage of the air conditioning system at low cost.

A reference example of a safety system comprises: a plurality of valve units used for a heat pump system, each of the valve units having at least one liquid refrigerant pipe portion, at least one gas refrigerant pipe portion, at least one liquid control valve disposed in the liquid refrigerant pipe portion, at least one gas control valve disposed in the gas refrigerant pipe portion, a casing accommodating at least the liquid control valve and the gas control valve and formed with at least two openings, and a refrigerant leakage detector configured to detect an occurrence of a refrigerant leakage in an internal space of the casing; a connection structure connecting the internal spaces of the casings via the openings; and a discharge structure connected to the connection structure or one of the casings, and configured to discharge air from the internal space of the casing in which a refrigerant leakage has occurred.

If separated casings are arranged for a plurality of valve units, it is burdensome and takes time to open each of the casings to check whether a refrigerant leakage has occurred in any casing. Furthermore, if a refrigerant leakage has occurred in any casing, the internal space of the casing would have already been permeated with a significant amount of leaked refrigerant when the monitoring/maintenance person arrives to open the casing. For instance, some refrigerants used are flammable or slightly flammable. Thus, opening such a casing is undesirable from safety perspective. In this regard, with the above configuration, even if a refrigerant leakage has occurred at a valve in any one of the valve units, the casing accommodating the valve can prevent or restrain the leaked refrigerant from spreading to the surrounding area. Moreover, concentration of the leaked refrigerant in the internal space of the casing can be decreased by discharging the air from the internal space to an external space of the casings. Furthermore, each casing can be substantially closed during a normal operation of the heat pump system, and a refrigerant leakage detection can be made based on concentration of refrigerant in this substantially closed space.

Thus, it is possible to swiftly detect an occurrence of a refrigerant leakage in the valve unit and start operation of the discharge structure at an early stage. Thereby, it is possible to prevent concentration of the leaked refrigerant in both the casing in which the refrigerant leakage has occurred and the surrounding area of the casing from becoming high in a more secure manner. This allows the monitoring/maintenance person to safely monitor, maintain, or repair the valves. Accordingly, it is possible to improve safety of the heat pump system regarding refrigerant leakage.

In addition, the discharge structure is used in common for the plurality of valve units. Hence, the safety of the heat pump system can be improved while preventing an increase in the installation cost of the system even in a case where the valves are arranged in separate locations.

Here, the external space to which the air is discharged by the discharge structure is preferably not an outer space directly surrounding any casing or an indoor space where a human or animal could come or reside. The external space is preferably an outdoor space. The heat pump system to which a plurality of the valve units belong may include a plurality of separate heat pump circuits. In other words, the pipings of the valve units need not necessary be connected to each other. In each of the valve units, the pipe portions, the valves, and the casing may be manufactured together. Thereby, it becomes easier to design the valve unit so as to enhance its performance such as airtightness of the casing. It also becomes easier to optimize the dimension of the valve unit, and a position of a maintenance door of the casing. Hence, it is possible to improve not only safety but also maintainability and functionality of the valve unit. Alternatively, the casing may be a retrofitted casing which is to be assembled around existing valves.

According to a preferred modification of the safety system mentioned above, the discharge structure includes a shared duct connected to the connection structure or one of the casings, and a ventilator disposed to the shared duct.

With the above configuration, it is possible to effectively discharge the air from the internal space of the casing when a refrigerant leakage in the casing has occurred. Here, the ventilator may be configured to blow air to push the air within the casing out, or suck air to draw the air in the casing out. The shared duct may be extended to the outdoor space, and the ventilator may be disposed in or attached to the shared duct. The ventilator may be configured to further discharge air surrounding at least one of the casings, e.g. air in a ceiling or a pipe shaft.

According to another preferred modification of the safety system mentioned above with the shared duct and the ventilator, the shared duct has a first end and a second end; the ventilator is disposed to the shared duct at or close to the second end, and configured to draw air in the shared duct towards the second end; and the shared duct is connected to the connection structure or one of the casings on a side of the first end with respect to the ventilator.

With the above configuration, the internal spaces of the casings, the connection structure, and the most part of the shared duct are kept in under pressure when the air is discharged. Thus, it is possible to prevent the air containing refrigerant from leaking to the surrounding area.

According to further another preferred modification of the safety system mentioned above with the second end of the shared duct, the second end of the shared duct is open to an outdoor space.

With the above configuration, the air containing refrigerant can be discharged to the outdoor space. Thus, the safety of the heat pump system can be further improved.

According to further another preferred modification of any one of the safety systems mentioned above with the shared duct and the ventilator, the safety system further includes: a controller configured to control the ventilator to start operating when a refrigerant leakage in any one of the valve units has occurred.

With the above configuration, it is possible to discharge the air containing refrigerant in a more secure manner when the refrigerant leakage has occurred.

According to further another preferred modification of any one of the safety systems mentioned above with a controller, each of the refrigerant leakage detectors are configured to output detection result information; and the controller is configured to receive the detection result information outputted from any one of the refrigerant leakage detectors, and identify in which of the valve units a refrigerant leakage has occurred based on the received detection result information.

With the above configuration, it is possible to identify the valve unit in which a refrigerant leakage has occurred, and perform a control of the ventilator based on the determination result. Here, the detection result information indicates whether or not a refrigerant leakage in the corresponding valve unit has occurred, and may indicate an identification of the valve unit in which the refrigerant leakage has occurred (hereinafter referred to as “the valve unit of refrigerant leakage”).

According to further another preferred modification of any one of the safety systems mentioned above with the shared duct and the ventilator, the at least two openings of each of the casings include a first opening and a second opening: and the connection structure includes a plurality of individual ducts connected to the second openings of the casings, respectively, and further connected to the shared duct in common.

With the above configuration, the internal spaces of the casings are connected to each other in parallel. In other words, each of the internal spaces communicates with the discharge structure without being interposed by any other casing. Hence, it is possible to reduce static pressure capacity required of the ventilator.

According to further another preferred modification of any one of the safety systems mentioned above with the individual ducts, each of the valve units further has a damper configured to block air to pass through the first opening when the damper is closed, and allow air to pass through the first opening when the damper is open; and the controller is configured to control the dampers such that, when the ventilator operates due to the occurrence of the refrigerant leakage, the damper of the valve unit in which the refrigerant leakage has occurred is open while the damper of the valve unit in which no refrigerant leakage has occurred is closed.

It is preferable that all the dampers are closed during a normal operation of the heat pump system to swiftly detect a refrigerant leakage and prevent the leaked refrigerant from spreading out towards the surrounding area. Meanwhile, if the damper is closed, the first opening cannot work as an intake port of an external air or an exhaust port of the internal air, and it is difficult to replace air in the internal space of the casing even if the ventilator operates. In this regard, the above configuration opens the damper of the valve unit of refrigerant leakage to effectively discharge air while achieving a swift detection of a refrigerant leakage. Moreover, the other damper or dampers are kept closed, and thereby the valve unit subject to the air discharge can be limited to the valve unit of refrigerant leakage. In general, it is rare that refrigerant leakages occur in different valve units at a time. Hence, it is possible to reduce air volume capacity required of the ventilator. Each of the dampers may be directly attached to the first opening or arranged away from the first opening and connected to the first opening via a duct.

According to further another preferred modification of any one of the safety systems mentioned above with the individual ducts and the dampers, the controller includes a plurality of unit controllers disposed in the valve units, respectively, and a central controller configured to communicate with the unit controllers; each of the refrigerant leakage detectors is configured to transmit detection result information to the central controller via the corresponding unit controller; and the central controller is configured to determine whether a refrigerant leakage in any one of the valve units has occurred based on the detection result information received from the valve unit, and, when the refrigerant leakage has occurred in any one of the valve units, transmit a damper open command to the damper of the valve unit in which the refrigerant leakage has occurred via the corresponding unit controller and control the ventilator to start operating.

With the above configuration, it is possible to identify the valve unit of refrigerant leakage, and perform a centralized control of the ventilator and the dampers based on the determination result in a more secure manner. Here, the detection result information indicates whether or not a refrigerant leakage in the valve unit has occurred, and may indicate an identification of the valve unit of refrigerant leakage. The damper open command instructs the damper to open, and may designate an identification of the valve unit of which the damper should open.

According to further another preferred modification of any one of the safety systems with the shared duct and the ventilator, the at least two openings of each of the casings include a first opening and a second opening; the connection structure includes at least one connecting duct connected on one side to the second opening of one of the casings and connected on another side to the first opening of another one of the casings; and the shared duct of the discharge structure is connected to the second opening of one of the casings to which there is no connecting duct connected.

With the above configuration, the internal spaces of the casings are connected to the discharge structure in series. In other words, at least one of the internal spaces communicates with the discharge structure via one or more of the other casings. Thereby, it is possible to reduce the total length of ducts for connecting the casings to the discharge structure, and thus reduce the installation cost of the system. The shared duct and the ventilator may be integrated as a single element. If one of the casings has a part exposed to the outdoor space, such a single element may be disposed in this part.

According to further another preferred modification of any one of the safety systems mentioned above with the connecting duct, each of the valve units further has a damper configured to block air to pass through the first opening when the damper is closed, and allow air to pass through the first opening when the damper is open; and the controller is configured to control the dampers of all the valve units to be open when the ventilator operates due to the occurrence of the refrigerant leakage.

It is preferable that all the dampers are closed during a normal operation of the heat pump system to swiftly detect a refrigerant leakage and prevent the leaked refrigerant from spreading out towards the surrounding area. Meanwhile, if the damper of any one of the casings is closed, the first openings of the casings continuing in series cannot work as an intake port of an external air or an exhaust port of the internal air, and it is difficult to replace air in their internal space even if the ventilator operates. In this regard, the above configuration opens the dampers of all the valve units continuing in series to effectively discharge air while achieving a swift detection of a refrigerant leakage. Each of the dampers may be directly attached to the first opening or arranged away from the first opening and connected to the first opening via a duct.

According to further another preferred modification of any one of the safety systems mentioned above with the connecting duct and the dampers, the controller includes a plurality of unit controllers disposed in the valve units, respectively, and a central controller configured to communicate with the unit controllers; each of the refrigerant leakage detectors is configured to transmit detection result information to the central controller via the corresponding unit controller; and the central controller is configured to determine whether a refrigerant leakage in any one of the valve units has occurred based on the detection result information received from the valve unit, and, when the refrigerant leakage has occurred, transmit a damper open command to the dampers of all the valve units via the unit controllers and control the ventilator to start operating.

With the above configuration, it is possible to detect an occurrence of refrigerant leakage in any valve unit to perform a centralized control of the ventilator and the dampers in a more secure manner. Here, the detection result information indicates whether or not a refrigerant leakage in the valve unit has occurred, and may indicate an identification of the valve unit of refrigerant leakage. The damper open command instructs the damper to open, and may designate an identification of the valve unit of which the damper should open.

A reference example of a method for assembling any one of the safety systems mentioned above, wherein the casing is formed from a plurality of casing parts, comprises: arranging, for each of the valve units, the corresponding casing parts around at least the liquid control valve and the gas control valve of the valve unit; fixing, for each of the valve units, the corresponding casing parts to each other; disposing, for each of the valve units, the refrigerant leakage detector, arranging the connection structure so as to connect the internal spaces of the casings; and connecting the discharge structure to the connection structure or one of the casings.

By the above method, it is possible to obtain the safety system mentioned above even with an existing heat pump system.

A reference example of an air conditioning system comprises: any one of the safety systems mentioned above, a heatsource-side unit including a compressor and a heatsource-side heat exchanger; a plurality of utilization-side units each including a utilization-side heat exchanger; a liquid refrigerant piping extending between the heatsource-side unit and the utilization-side units, and including the liquid refrigerant pipe portions; a gas refrigerant piping extending between the heatsource-side unit and the utilization-side units, and including the gas refrigerant pipe portions; and an expansion mechanism disposed in the liquid refrigerant piping.

With the above configuration, it is possible to obtain air conditioning system with high safety regarding refrigerant leakage at valves.

According to a preferred modification of the air conditioning system mentioned above which includes the controller, the air conditioning system further comprises: a system controller configured to control an air conditioning operation of the air conditioning system, wherein at least part of the controller of the safety system is a part of the system controller.

With the above configuration, it is possible to integrate at least a part of the controller for air conditioning and at least a part of the system controller for the operation of the safety system. Thereby, the total installation cost can be reduced. The integrated part of the system controller may be separated away from the other part of the system controller.

According to another preferred modification of any one of the air conditioning systems mentioned above which includes the ventilator, the air conditioning system further comprises: a plurality of sections each including the plurality of valve units, the connection structure, and the discharge structure, wherein the controller is configured to control the ventilator of only the section in which a refrigerant leakage has occurred to start operating.

With the above configuration, it is possible to integrate the controllers for a plurality of the safety systems each having the connection structure and the discharge structure. Thereby, the total installation cost can be reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration diagram of an air conditioning system with valve units according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a valve unit shown in FIG. 1 .

FIG. 3 is a schematic configuration diagram of a safety system according to the first embodiment.

FIG. 4 is a flow chart indicating an operation performed by a unit controller shown in FIG. 3 .

FIG. 5 is a flow chart indicating an operation performed by a central controller shown in FIG. 3 .

FIG. 6 is a schematic configuration diagram of the safety system according to a second embodiment of the present invention.

FIG. 7 is a flow chart indicating an operation performed by a central controller shown in FIG. 6 .

FIG. 8 is a schematic configuration diagram of the safety system according to a third embodiment of the present invention.

FIG. 9 is a grouping table used by a central controller shown in FIG. 9 .

FIG. 10 is a schematic configuration diagram of the safety system according to a fourth embodiment of the present invention.

FIG. 11 is a grouping table used by the central controller according to a fourth embodiment of the present invention.

FIG. 12 is a schematic configuration diagram of a valve unit according to a modification of the present embodiment.

FIG. 13 is a schematic configuration diagram of an air conditioning system according to a fifth embodiment of the present invention.

FIG. 14 is a schematic configuration diagram of a safety system of the air conditioning system shown in FIG. 13 .

FIG. 15 is a flow chart indicating an operation performed by a central controller shown in FIG. 14 .

FIG. 16 is a schematic configuration diagram of a safety system according to a first variation of the fifth embodiment.

FIG. 17 is a schematic configuration diagram of a safety system according to a second variation of the fifth embodiment.

FIG. 18 is a schematic configuration diagram of a safety system according to a third variation of the fifth embodiment.

FIG. 19 is a schematic configuration diagram of an air conditioning system according to a sixth embodiment of the present invention.

FIG. 20 is a schematic configuration diagram of an example of a safety system of the air conditioning system shown in FIG. 19 .

FIG. 21 is a flow chart indicating an operation performed by a central controller shown in FIG. 20 .

FIG. 22 is a schematic configuration diagram of an air conditioning system according to a seventh embodiment of the present invention.

FIG. 23 is a schematic configuration diagram of a variation of the safety system according to any one of the fifth to seventh embodiments.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of an air conditioning system and a safety system according to the present invention will be described with reference to the drawings.

First Embodiment

(Configuration of Air Conditioning System)

The air conditioning systems according to a first embodiment of the present embodiment is a multi air conditioning system with a so-called three-pipe configuration, which includes a heatsource-side unit and a plurality of utilization-side units.

FIG. 1 is a schematic configuration diagram of the air conditioning system according to the first embodiment.

As shown in FIG. 1 , the air conditioning system 100 comprises a heatsource-side unit 110, and a plurality of utilization-side units 120 connected to the heatsource-side unit 110 via refrigerant pipes. The utilization-side units 120 are divided into a plurality of unit families 121, e.g. first to third unit families 121_1, 121_2, 121_3. Yet, the number of the unit families 121 is not limited to three, and may be two, four, or more. The number of the utilization-side unit 120 belonging to each of the unit families 121 is also not limited.

The heatsource-side unit 110 includes a compressor, and a condenser and an evaporator (heatsource-side heat exchangers) (not shown). The heatsource-side unit 110 also extends out a liquid refrigerant pipe 131, a low-pressure gas refrigerant pipe 132, and a high-pressure gas refrigerant pipe 133. The liquid refrigerant pipe 131 communicates with each of the condenser and the evaporator. The low-pressure gas refrigerant pipe 132 communicates with a suction port of the compressor. The high-pressure gas refrigerant pipe 133 communicates with a discharge port of the compressor.

The liquid refrigerant pipe 131 branches into a plurality of heatsource-side liquid pipes 141 towards the first to third unit families 121_1, 121_2, 121_3. The low-pressure gas refrigerant pipe 132 branches into a plurality of heatsource-side low-pressure gas pipes 142 towards the first to third unit families 121_1, 121_2, 121_3. The high-pressure gas refrigerant pipe 133 branches into a plurality of heatsource-side high-pressure gas pipes 143 towards the first to third unit families 1211, 1212, 121_3.

For each of the unit families 121, the heatsource-side liquid pipe 141 branches into a plurality of utilization-side liquid refrigerant pipes 151 towards the utilization-side units 120 which belong to the unit family 121. For each of the unit families 121, the heatsource-side low-pressure gas pipe 142 branches into a plurality of utilization-side gas refrigerant pipes 152 towards the utilization-side units 120 which belong to the unit family 121. For each of the unit families 121, the heatsource-side high-pressure gas pipe 143 branches towards the utilization-side units 120 which belong to the unit family 121, and each of the branched pipes merges with the corresponding utilization-side gas refrigerant pipe 152.

Each of the utilization-side units 120 includes a utilization-side heat exchanger (not shown). For each of the utilization-side units 120, the utilization-side heat exchanger communicates with the corresponding utilization-side liquid refrigerant pipe 151 and utilization-side gas refrigerant pipe 152.

In other words, in the air conditioning system 100, a liquid refrigerant piping and a gas refrigerant piping extends between the heatsource-side unit 110 and the utilization-side units 120, while branching towards the unit families 121 and then towards the utilization-side units 120 in each of the unit families 121, to form a heat pump circuit. Thereby, it is possible to supply hot/cold heat from the heatsource-side unit 110 to each of the utilization-side units 120 by circulating refrigerant.

The air conditioning system 100 further includes first to third valve units 200_1, 200_2, 200_3 for the first to third unit families 121_1, 121_2, 120_3, respectively. For each of the unit families 121, the branching points towards the corresponding utilization-side units 120 are disposed in the corresponding valve unit 200. The first to third valve units 200_1, 200_2, 200_3 have a substantially same configuration. Thus, in the following descriptions, the term “the valve unit 200” means any one of the first to third valve units 200_1, 200_2, 200_3. The details of the valve unit 200 are explained hereinafter.

The air conditioning system 100 includes a safety system for improving safety of the air conditioning system 100 (a heat pump system) regarding refrigerant leakage. The first to third valve units 200_1, 200_2, 200_3 are part of the safety system. The details of the safety system will be explained later.

(Configuration of Valve Unit)

FIG. 2 is a schematic configuration diagram of the valve unit 200.

As shown in FIG. 2 , the valve unit 200 comprises a multi branch selector 300, a casing 400, a damper 440, a refrigerant leakage detector 500, and a unit controller 600. The casing 400 accommodates the multi branch selector 300 therein. The refrigerant leakage detector 500 and the unit controller 600 are disposed in an internal space 401 of the casing 400. Yet, the unit controller 600 may be disposed on or outside the casing 400.

The multi branch selector 300 includes a heatsource-side liquid pipe portion 310, a plurality of utilization-side liquid pipe portions 311, a low-pressure gas pipe portion 320, a plurality of low-pressure gas sub pipes 321, a plurality of utilization-side gas pipe portions 330, a high-pressure gas pipe portion 340, a plurality of high-pressure gas sub pipes 341, a plurality of bypass pipes 351, and a plurality of refrigerant heat exchangers 352. The multi branch selector 300 further includes a plurality of low-pressure gas control valves 361, a plurality of high-pressure gas control valves 362, a plurality of expansion mechanisms 363, a plurality of liquid shut-off valves 364, and a plurality of gas shut-off valves 365.

The numbers of the utilization-side liquid pipe portions 311, the low-pressure gas sub pipes 321, the utilization-side gas pipe portions 330, the high-pressure gas sub pipes 341, the bypass pipes 351, the refrigerant heat exchangers 352, the low-pressure gas control valves 361, the high-pressure gas control valves 362, the expansion mechanisms 363, the liquid shut-off valves 364, and the gas shut-off valves 365 may be the same as the number of the utilization-side units 120 which belong to the corresponding unit family 121 (see FIG. 1 ).

The heatsource-side liquid pipe portion 310, the low-pressure gas pipe portion 320, the high-pressure gas pipe portion 340 are parts of the corresponding heatsource-side liquid pipe 141, heatsource-side low-pressure gas pipe 142, and heatsource-side high-pressure gas pipe 143 (see FIG. 1 ). The utilization-side liquid pipe portions 311 are parts of the corresponding utilization-side liquid refrigerant pipes 151 (see FIG. 1 ). The low-pressure gas sub pipes 321, the high-pressure gas sub pipes 341, and the utilization-side gas pipe portions 330 are parts of the corresponding utilization-side gas refrigerant pipes 152 (see FIG. 1 ). One of the utilization-side liquid pipe portions 311 and one of the utilization-side gas pipe portions 330 communicate with the same utilization-side heat exchanger of one of the utilization-side units 120.

In the multi branch selector 300, the heatsource-side liquid pipe portion 310 branches into the utilization-side liquid pipe portions 311, the low-pressure gas pipe portion 320 branches into the low-pressure gas sub pipes 321, and the high-pressure gas pipe portion 340 branches into the high-pressure gas sub pipes 341. One of the low-pressure gas sub pipes 321 and one of the high-pressure gas sub pipes 341 are connected to one of the utilization-side gas pipe portions 330. It can also be said that each of the low-pressure gas pipe portion 320 branches into the utilization-side gas pipe portions 330 via the low-pressure gas sub pipes 321, and that the high-pressure gas pipe portion 340 branches into the utilization-side gas pipe portions 330 via the high-pressure gas sub pipes 341. It can also be said that each of the utilization-side gas pipe portions 330 branches into the low-pressure gas pipe portion 320 and the high-pressure gas pipe portion 340 via one of the low-pressure gas sub pipes 321 and one of the high-pressure gas sub pipes 341.

The bypass pipes 351 are connected to the utilization-side liquid pipe portions 311, respectively, and each connected to the low-pressure gas pipe portion 320. In other words, one of the bypass pipes 351 branches from one of the utilization-side liquid pipe portions 311 and merges with the low-pressure gas pipe portion 320.

The expansion mechanisms 363 are disposed in the bypass pipes 351, respectively. Each of the expansion mechanisms 363 is configured to decompress and expand refrigerant flowing from the corresponding utilization-side liquid pipe portion 311 in the bypass pipe 351. Each of the expansion mechanisms 363 may be an electric expansion valve.

The refrigerant heat exchangers 352 are provided to the bypass pipes 351, respectively. Each of the refrigerant heat exchangers 352 is configured to cause a heat-exchange between refrigerant flowing in one of the utilization-side liquid pipe portions 311 and refrigerant flowing in the corresponding bypass pipe 351 that has been decompressed and expanded by the corresponding expansion mechanism 363. In other words, each of the refrigerant heat exchangers 352 forms a subcooling system in combination with the corresponding utilization-side liquid pipe portion 311, bypass pipe 351, and expansion mechanism 363. Each of the refrigerant heat exchangers 352 may have two flow channels which form a part of the utilization-side liquid pipe portion 311 and a part of the bypass pipe 351, respectively, and have thermal conductance therebetween.

The low-pressure gas control valves 361 are disposed in the low-pressure gas sub pipes 321, respectively. Each of the low-pressure gas control valves 361 is configured to switch between an open state and a closed state, i.e. whether or not to allow refrigerant to flow between the low-pressure gas pipe portion 320 and the corresponding utilization-side gas pipe portion 330. The state of each of the low-pressure gas control valves 361 is controlled by the unit controller 600 in accordance with an operation mode desired for the corresponding utilization-side unit 120. Each of the low-pressure gas control valves 361 may be an electric valve.

The high-pressure gas control valves 362 are disposed in the high-pressure gas sub pipes 341, respectively. Each of the high-pressure gas control valves 362 is configured to switch between an open state and a closed state, i.e. whether or not to allow refrigerant to flow between the high-pressure gas pipe portion 340 and the corresponding utilization-side gas pipe portion 330. The state of each of the high-pressure gas control valves 362 is controlled by the unit controller 600 in accordance with an operation mode desired for the corresponding utilization-side unit 120. Each of the high-pressure gas control valves 362 may be an electric valve, and preferably formed with a minute channel.

The liquid shut-off valves 364 are disposed in the utilization-side liquid pipe portions 311, respectively. The gas shut-off valves 365 are disposed in the utilization-side gas pipe portions 330, respectively. The liquid shut-off valve 364 and the gas shut-off valve 365 disposed in the utilization-side liquid pipe portion 311 and the utilization-side gas pipe portion 330 which communicate with the same utilization-side heat exchanger define a utilization-side piping section which extends therebetween and includes at least the utilization-side heat exchanger. Each of the liquid shut-off valves 364 and the gas shut-off valves 365 may be an electric valve.

The casing 400 may have a substantially box shape, and is large enough to accommodate at least the multi branch selector 300 and the refrigerant leakage detector 500 therein. The casing 400 may be made of metal plates, carbon fibre plates, fire-retardant resin plates, or the like. The casing 400 is formed with a plurality of pipe apertures 410.

The plurality of pipe apertures 410 are configured to allow the pipes extending from the multi branch selector 300 (hereinafter referred to as “the extending pipes”) to pass therethrough, respectively. In other words, the plurality of pipe apertures 410 are formed at positions corresponding to the positions of the extending pipes, and each have diameter greater than the diameter of the corresponding extending pipe. Here, such extending pipes include the heatsource-side liquid pipe portion 310, the low-pressure gas pipe portion 320, the high-pressure gas pipe portion 340, the utilization-side liquid pipe portions 311, and the utilization-side gas pipe portions 330.

Each of the extending pipes may have a pipe connection part 370 for being connected to the corresponding outer pipes, i.e. the other part of the corresponding heatsource-side liquid pipe 141, heatsource-side low-pressure gas pipe 142, heatsource-side high-pressure gas pipe 143, utilization-side liquid refrigerant pipe 151, or utilization-side gas refrigerant pipe 152 (see FIG. 1 ). It is preferable that the pipe connection parts 370 are arranged outside of the casing 400.

The casing 400 is further formed with a first opening 420, and a second opening 430. It is preferable that the first opening 420 and the second opening 430 are arranged on opposite sides of the casing 400 with respect to the center part of the internal space 401.

Especially when refrigerant heavier than atmospheric air such as R32 refrigerant is used, it is preferable that both the first opening 420 and the second opening 430 are arranged closer to the top part of the casing 400. Thereby, it is possible to prevent leaked refrigerant from spreading out to the surrounding area of the casing 400 in a more secure manner, and thereby swiftly detect an occurrence of a refrigerant leakage in the casing 400. Yet, it might also be an option to arrange the first opening 420 closer to the bottom part of the casing 400 while arranging the second opening 430 closer to the top part of the casing 400 such that refrigerant accumulated at the bottom can be effectively discharged. In any cases, the arrangement of the first opening 420 and the second opening 430 is not limited to the above.

The damper 440 is directly attached to the first opening 420. Alternatively, the damper 440 may be arranged away from the first opening 420 inside or outside the casing 400, and connected to the first opening 420 via a duct. The damper 440 is configured to block air to pass through the first opening 420 when the damper 440 is closed and allow air to pass through the first opening 420 when the damper 440 is open. More specifically, the damper 440 includes a flap 441, and an electric motor (not shown) for moving the flap to switch between a closed position in which the flap closes off the first opening 420 and an open position in which the flap does not close off the first opening 420. The motor is controlled by the unit controller 600 as explained later. As shown in FIG. 2 . the damper 440 may be a normally closed damper which is closed during a normal operation of the air conditioning system 100, i.e. when no refrigerant leakage has occurred.

The second opening 430 is configured to allow air to pass therethrough between the internal space 401 and an external space outside the casing 400. As explained later, a duct is connected to second opening 430 on the outside of the casing 400. The second opening 430 may be provided with a damper which is controlled to move synchronously with the damper 440 of the first opening 420.

It is also preferable that the casing 400 has a maintenance door configured to allow a monitoring/maintenance person to check the states of the multi branch selector 300, the refrigerant leakage detector 500, and the unit controller 600, and/or repair them through the opened door, as necessary.

Insulators 450 are applied to the casing 400 such that the internal space 401 of the casing 400 is substantially isolated from the external space outside the casing 400 at the parts other than the first opening 420 and the second opening 430. The insulators 450 may include tubular insulators fitted into the gaps between outer surfaces of the extending pipes of the multi branch selector 300 and inner edges of the pipe apertures 410, respectively. Each insulator 450 may be a foam tube, a foam wrap, a foam filler, a caulk, a tape, or the like. The foam tube with a cut line extending in its axis direction is easy to fit into the gap. The thickness of the foam tube is preferably equal to or slightly greater than the clearance between the outer surface of the corresponding extending pipe and the inner surface of the corresponding pipe aperture 410. The insulators 450 may be attached to the extending pipes before assembling the casing 400.

The insulators 450 may also be applied to other gaps in the casing 400, such as the gap between the flap 441 in the closed position and a housing of the damper 440, the gap between the housing of the damper 440 and edges of first opening 420, and the gap between the maintenance door and a door frame of the casing 400.

The refrigerant leakage detector 500 is configured to detect an occurrence of a refrigerant leakage in the internal space 401 of the corresponding casing 400. The refrigerant leakage detector 500 is configured to detect a concentration of the refrigerant in an air surrounding the refrigerant leakage detector 500, and continuously or regularly output a detector signal indicating a detection value Vs which corresponds to the detected concentration to the unit controller 600. The refrigerant leakage detector 500 may be a semi-conductor gas sensor reactive to the refrigerant used in the air conditioning system 100. In a case where refrigerant which is heavier than atmospheric air, such as R32 refrigerant, the refrigerant leakage detector 500 is preferably disposed in the internal space 401 at or close to an inner bottom surface of the casing 400.

As mentioned later, it is determined by the unit controller 600 whether a refrigerant leakage in the corresponding casing 400 (hereinafter referred to as “the refrigerant leakage”) has occurred based on the detection value Vs of the refrigerant leakage detector 500. Thus, the detection value Vs is detection result information indicating whether the refrigerant leakage in the corresponding valve unit 200 has occurred.

The unit controller 600 is configured to control operation of the valve unit 200 via wired communication paths and/or wireless communication paths (partially not shown) between the unit controller 600 and the machineries in the valve unit 200. In particular, the unit controller 600 is configured to receive the detector signal from the refrigerant leakage detector 500 and determine whether the refrigerant leakage has occurred based on the detector signal. When it is determined that the refrigerant leakage has occurred, the unit controller 600 is configured to output a leakage signal to a later-mentioned central controller. A leakage signal indicates a unit ID (identification) of the valve unit 200 in which the leakage detector 500 is disposed, and indicates that the refrigerant leakage has occurred in the valve unit 200 of the unit ID indicated by the leakage signal. In other words, a leakage signal is detection result information indicating whether the refrigerant leakage in the corresponding valve unit 200 has occurred.

The unit controller 600 is also configured to receive a later mentioned damper open command from the central controller. When the unit controller 600 has received the damper open command designating the unit ID of the valve unit 200 to which the unit controller 600 belongs to, control the damper 440 to open.

The unit controller 600 may be further configured to switch the open/closed state of each of the low-pressure gas control valves 361 and high-pressure gas control valves 362, and/or control the opening degree of each of the expansion mechanisms 363 (see FIG. 2 ) such that desired cooling/heating operation can be performed in each of the utilization-side units 120 (see FIG. 1 ).

For instance, for the utilization-side unit 120 which should perform cooling operation, the corresponding low-pressure gas control valve 361 is opened and the corresponding high-pressure gas control valve 362 and expansion mechanism 363 are closed. For the utilization-side unit 120 which should perform heating operation, the corresponding high-pressure gas control valve 362 and expansion mechanism 363 are opened and the corresponding low-pressure gas control valve 361 is closed. The unit controller 600 may perform such an operation based on signals which indicate the desired operation modes of the corresponding utilization-side units 120. Such signals may be sent from the heatsource-side unit 110, the corresponding utilization-side units 120, and/or an information output device (not shown) used by the monitoring/maintenance person.

The unit controller 600 may be separated into a first controller having the functions for controlling the multi branch selector 300 and a second controller having the functions for determining the refrigerant leakage, controlling the damper 440. In this case, it is also preferable that the first and second controllers have different electricity sources.

The unit controller 600 includes an arithmetic circuit such as a CPU (Central Processing Unit), a work memory used by the CPU such as a RAM (Random Access Memory), and a recording medium storing control programs and information used by the CPU such as a ROM (Read Only Memory), although they are not shown. The unit controller 600 is configured to perform information processing and signal processing by the CPU executing the control programs to control the operation of the valve unit 200.

The casing 400, the first opening 420, the second opening 430, the damper 440, the insulators 450, the refrigerant leakage detector 500, and the unit controller 600 are part of the safety system of the air conditioning system 100.

(Configuration of Safety System)

FIG. 3 is a schematic configuration diagram of the safety system according to the first embodiment.

As shown in FIG. 3 , the safety system 700 of the air conditioning system 100 according to the first embodiment comprises the first to third valve units 200_1, 200_2, 200_3, first to third individual ducts 710_1 to 710_3, a shared duct 720, a ventilator 730, and a central controller 800. The first to third valve units 200_1, 200_2, 200_3 have the first to third internal spaces 401_1, 401_2, 401_3 of the first to third casings 400_1, 400_2, 400_3, respectively. Here, the multi branch selectors 300 of the first to third valve units 200_1, 200_2, 200_3 (see FIG. 2 ) are omitted.

The first to third individual ducts 710_1 to 710_3 correspond to the first to third valve units 200_1, 200_2, 200_3, respectively. The first to third individual ducts 710_1 to 710_3 have a substantially same configuration with respect to the corresponding individual duct 710. Thus, in the following descriptions, the term “the individual duct 710” means any one of the first to third individual ducts 710_1 to 710_3. The individual duct 710 is connected to the second opening 430 of the casing 400 of the corresponding valve unit 200 at one end of the individual duct 710. The individual duct 710 is further connected to the shared duct 720 at another end of the individual duct 710. In other words, the first to third individual ducts 710_1 to 710_3 are connected to the shared duct 720 in common.

The ventilator 730 is disposed to the shared duct 720 at or close to one end (hereinafter referred to as “the second end”) of the shared duct 720, and configured to draw air in the shared duct 720 towards the second end. It is preferable that the second end of the shared duct 720 is open to an outdoor space. It is also preferable that the ventilator 730 is disposed at the second end as shown in FIG. 3 . The operation of the ventilator 730 is controlled by the central controller 800. For instance, the ventilator 730 starts operating when the ventilator 730 has received a ventilator start command from the central controller 800. The ventilator 730 may be a fan. The ventilator 730 may be provided with a check air damper which is configured to prevent an air from passing through the ventilator 730 when the ventilator 730 is not in operation.

The shared duct 720 is connected to the first to third individual ducts 710_1 to 710_3 on a side of another end (hereinafter referred to “the first end”) of the shared duct 720 with respect to the ventilator 730. Thus, the whole structure of the first to third individual ducts 710_1 to 710_3 and the shared duct 720 forms a branching duct. Any one of the branching parts of this structure may be deemed as the first end of the shared duct 720. For instance, the part between the point branching towards the first valve unit 200_1 and the point branching towards the second valve unit 200_2 may be deemed as any one of a part of the shared duct 720, a part of second individual duct 710_2, and a part of third individual duct 710_3.

Hence, the first to third individual ducts 710_1 to 710_3 form a connection structure which connects the first to third internal spaces 4011, 401_2, 401_3 via the first to third second openings 430_1, 4302, 4303, respectively. As for the first openings 420, an extension duct may be connected to each of all or part of the first openings 420 on the outer side of the corresponding casing 400.

When any one of the first to third dampers 440_1, 440_2, 440_3 is open, an air path AP can be formed that extends from an external space outside the corresponding casing 400 to the ventilator 730. This air path AP passes through the first opening 420 with the damper 440 open, the corresponding internal space 401, second opening 430 and individual duct 710, and the shared duct 720. If the ventilator 730 operates in this state, the air in the internal space 401 of the casing 400 with the damper 440 open is discharged by the suction force of the ventilator 730. Meanwhile, as for the casing 400 with the damper 440 closed, the above air path AP is not formed. Thus, even if the ventilator 730 operates, the air in the internal space 401 of the casing 400 with the damper 440 closed is not discharged by the suction force of the ventilator 730. FIG. 3 depicts a situation where only the first damper 440_1 is open.

Hence, the shared duct 720 and the ventilator 730 form a discharge structure which is connected to the connection structure mentioned above and configured to discharge air from the internal space 401 of the casing 400 with the damper 440 open.

The central controller 800 is disposed in the heatsource-side unit 110 (see FIG. 1 ), for instance. The central controller 800 may be a part of a system controller (not shown) for controlling an air conditioning operation of the air conditioning system 100.

The central controller 800 is connected to the first to third unit controllers 6001, 600_2, 600_3 and the ventilator 730 via a communication path 801. The communication path 801 may serially connect the first to third unit controllers 600_1, 600_2, 600_3 and the ventilator 730 to the central controller 800 as shown in FIG. 3 by means of a wired and/or wireless communication.

When a refrigerant leakage has occurred in any one of the first to third valve units 200_1, 200_2, 200_3, the central controller 800 is configured to control the ventilator 730 to start operating (turn ON). Moreover, the central controller 800 is configured to, in cooperation with the first to third unit controllers 600_1, 600_2, 600_3, identify in which of the first to third valve units 200_1, 200_2, 200_3 the refrigerant leakage has occurred, and control the first to third dampers 440_1, 440_2, 440_3. More specifically, the central controller 800 is configured to control the first to third dampers 440_1, 440_2, 440_3 such that, when the ventilator 730 operates due to the occurrence of the refrigerant leakage, the damper 440 of the valve unit 200 of refrigerant leakage is open while the other dampers 440 are closed. Thereby, the discharge structure mentioned above can discharge air from the internal space 401 of the casing 400 with refrigerant leakage.

The central controller 800 includes an arithmetic circuit such as a CPU, a work memory used by the CPU such as a RAM, and a recording medium storing control programs and information used by the CPU such as a ROM, although they are not shown. The central controller 800 is configured to perform information processing and signal processing by the CPU executing the control programs to control at least the operation of the safety system of the air conditioning system 100.

(Operation of Unit Controller)

The unit controller 600 is configured to detect an occurrence of a refrigerant leakage in the corresponding casing 400. The unit controller 600 is further configured to, when the refrigerant leakage has occurred, inform of the detection result to the central controller 800 and control the corresponding damper 440 to open which is normally closed under control of the central controller 800. More specifically, the unit controller 600 is configured to perform the following operation.

FIG. 4 is a flow chart indicating an operation performed by the unit controller 600.

In step S1010, the unit controller 600 acquires the detection value Vs from the detector signal outputted from the refrigerant leakage detector 500. The unit controller 600 may passively receive the detector signal which is continuously or regularly outputted from the refrigerant leakage detector 500, or actively request the refrigerant leakage detector 500 to output the detector signal regularly. The obtained detection value Vs basically reflects the variation in the concentration of the refrigerant in the casing 400.

In step S1020, the unit controller 600 compares the detection value Vs acquired and a detection value threshold Vth, and determines whether the detection value Vs is less than the detection value threshold Vth. The unit controller 600 may obtain a moving average value of the detection values Vs in a certain time length to use the moving average value as the detection value Vs which is compared with the detection value threshold Vth.

The detection value threshold Vth is stored in the unit controller 600 in advance. The detection value threshold Vth may be a value determined by experiments or the like such that false detections and detection omissions of refrigerant leakages are avoided as much as possible. It is preferable that the detection value threshold Vth is set to a value less than a value corresponding to 25% of the Lower Flammability Limit (LFL) of the refrigerant used.

If the detection value Vs is equal to or greater than the detection value threshold Vth (S1020: No), the unit controller 600 proceeds to later-mentioned step S1030. If the detection value Vs is less than the detection value threshold Vth (S1020: Yes), the unit controller 600 proceeds to later-mentioned step S1040. It can be said that the refrigerant leakage detectors 500 transmits detection result information to the central controller 800 via the corresponding unit controller 600 by steps from S1010 to S1030.

In step S1030, the unit controller 600 transmits to the central controller 800 a leakage signal indicating the unit ID of the valve unit 200 to which the unit controller 600 belongs (hereinafter referred to as “the own unit ID”). The unit controller 600 may directly send a leakage signal to the central controller 800 or indirectly send a leakage signal to the central controller 800 via one or more of other unit controllers 600. In the latter case, the unit controllers 600 sends the leakage signal to the other unit controller 600, and the leakage signal is relayed in series by the unit controllers 600. For instance, when the communication path 801 is arranged as shown in FIG. 3 , the unit controller 600_3 of the third valve unit 200_3 directly sends a leakage signal to the central controller 800, and the unit controller 600_2 of the second valve unit 200_2 sends a leakage signal to the central controller 800 via the unit controller 600_3 of the third valve unit 200_3.

The unit controller 600 may determine the controller to which the leakage signal should be sent based on network information regarding the communication path between the unit control 600 and the central controller 800. The network information may be stored in the unit controller 600 in advance, or acquired by making an inquiry to the other unit controller or controllers 600 and/or the central controller 800.

In step S1040, the unit controller 600 determines whether a leakage signal has been received at the unit controller 600 that was transmitted from the other unit controller 600. If a leakage signal has been received (S1040: Yes), the unit controller 600 proceeds to step S1050. If a leakage signal has not been received (S1040: No), the unit controller 600 proceeds to later-mentioned step S1060.

In step S1050, the unit controller 600 forwards the received leakage signal towards the central controller 800. The unit controller 600 may directly send the received leakage signal to the central controller 800 or indirectly send the received leakage signal to the central controller 800 via one or more of other unit controllers 600. The unit controller 600 may determine the controller to which the received leakage signal should be sent based on the network information mentioned above.

In step S1060, the unit controller 600 determines whether a ventilator start command has been received at the unit controller 600. As mentioned later, a ventilator start command is a command transmitted from the central controller 800. If a ventilator start command has been received (S1060: Yes), the unit controller 600 proceeds to step S1070. If a ventilator start command has not been received (S1060: No), the unit controller 600 proceeds to later-mentioned step S1080.

In step S1070, the unit controller 600 forwards the received ventilator start command towards the ventilator 730. The unit controller 600 may directly send the received ventilator start command to the ventilator 730 or indirectly send the received ventilator start command to the ventilator 730 via one or more of other unit controllers 600. The unit controller 600 may determine the unit controller 600 to which the ventilator start command should be sent based on the network information mentioned above.

In step S1080, the unit controller 600 determines whether a damper open command has been received at the unit controller 600 that was transmitted from the central controller 800. If a damper open command has been received (S1080: Yes), the unit controller 600 proceeds to step S1090. If a damper open command has not been received (S1080: No), the unit controller 600 proceeds to later-mentioned step S1110.

In step S1090, the unit controller 600 further determines whether the received damper open command designates the valve unit 200 to which the unit controller 600 belongs (hereinafter referred to as “the own valve unit”) as the valve unit 200 which should open its damper 440. The unit controller 600 may make this determination based on whether the received damper open command designates the own unit ID. If the damper open command does not designate the own valve unit (S1090: No), the unit controller 600 proceeds to step S1100. If the damper open command designates the own valve unit (S1090: Yes), the unit controller 600 proceeds to later-mentioned step S1120.

In step S1100, the unit controller 600 forwards the received damper open command towards the other unit controller 600 which has not received the damper open command. The unit controller 600 may determine the unit controller 600 to which the received damper open command should be sent based on the network information mentioned above.

In step S1110, the unit controller 600 determines whether termination of operation has been designated. The designation may be made by a user operation, another device, or the unit controller 600 itself. If termination of the operation has not been designated (S1110: No), the unit controller 600 goes back to step S1010 to repeat the above acquisition and determination steps. If termination of the operation has been designated (S1110: Yes), the unit controller 600 terminates its operation.

In step S1120, the unit controller 600 controls the damper 440 of the own valve unit 200 to open, and then terminates its operation. For instance, the unit controller 600 controls the state of the damper 440 by controlling a supply of electricity thereto. The unit controller 600 may output alarm information by means of a sound, a light, a visual image, and/or a communication signal from a loudspeaker, an electric light, a display device, and/or a communication interface provided to the unit controller 600.

Steps S1040 and S1050 may be performed before steps S1010 to S1030. Steps S1080 to S1100 may also be performed before steps S1040 and S1050.

By the above operation, when a refrigerant leakage has occurred in the own valve unit 200, each of the unit controllers 600 can report to the central controller 800 the occurrence of the refrigerant leakage, and control the damper 440 of the own valve unit 200 to open when it has been instructed by the central controller 800.

(Operation of Central Controller)

The central controller 800 is configured to control the ventilator 730 to start operating when an occurrence of the refrigerant leakage in any one of the valve units 200 has been reported. The central controller 800 is further configured to control the damper 440 in the valve unit 200 of refrigerant leakage to open by instructing that to the corresponding unit controller 600. More specifically, the central controller 800 is configured to perform the following operation.

FIG. 5 is a flow chart indicating an operation performed by the central controller 800.

In step S2010, the central controller 800 determines whether a leakage signal has been received at the central controller 800 that was transmitted from one of the unit controllers 600. This leakage signal is a signal originated from the unit controller 600 in the step S1030 of FIG. 4 . If a leakage signal has been received (S2010: Yes), the central controller 800 proceeds to later-mentioned step S2030. If a leakage signal has not been received (S2010: No), the central controller 800 proceeds to later-mentioned step S2020.

In step S2020, the central controller 800 determines whether termination of operation has been designated. The designation may be made by a user operation, another device, or the central controller 800 itself. If termination of the operation has not been designated (S2020: No), the central controller 800 goes back to step S2010 to repeat the above determination step. If termination of the operation has been designated (S2020: Yes), the central controller 800 terminates its operation.

In step S2030, the central controller 800 obtains the unit ID indicated by the received leakage signal from the leakage signal. This unit ID indicates the originator of the leakage signal, i.e. the valve unit 200 of refrigerant leakage. Thereby, the central controller 800 can identify the valve unit 200 of refrigerant leakage.

In step S2040, the central controller 800 transmits a ventilator start command to the ventilator 730 to control the ventilator 730 to start operating. The ventilator start command may be directly sent to the ventilator 730 or relayed to it by the unit controller or controllers 600. For instance, the central controller 800 controls the operation of the ventilator 730 by controlling a supply of electricity thereto.

In step S2050, the central controller 800 transmits, to at least the originator of the received leakage signal, a damper open command designating the originator as the valve unit 200 which should open its damper 440. The central controller 800 may make this designation by using the unit ID of the originator. The damper open command may be directly sent to the unit controller 600 of the valve unit 200 of refrigerant leakage or relayed to it in series by the unit controller or controllers 600. Then, the central controller 800 terminates its operation. It can be said that the central controller 800 transmits the damper open command to the damper 440 of the valve unit 200 of refrigerant leakage via the corresponding unit controllers 600 by step S2050 and step S1120 of FIG. 4 .

The central controller 800 may output alarm information by means of a sound, a light, a visual image, and/or a communication signal from a loudspeaker, an electric light, a display device, and/or a communication interface provided to the central controller 800. In this case, it is preferable that the alarm information indicates the valve unit 200 of refrigerant leakage by outputting the unit ID of the valve unit 200 of refrigerant leakage or other information from which the valve unit 200 of refrigerant leakage can be identified, e.g. information indicating the location of the valve unit 200.

Step S2040 may be performed before step S2030, and step S2050 may also be performed before step S2040. Yet, it is preferable to start operation of the ventilator 730 before opening the corresponding damper 440. The central controller 800 may control the timing of transmission of the damper open command such that the corresponding damper 440 opens only when the performance of the ventilator 730 has reached a level high enough to prevent the internal air in the corresponding casing 400 from outflowing through the first opening 420 even if the damper 440 is opened.

By the above operation, when a refrigerant leakage in any one of the valve units 200 has occurred, the central controller 800 can control the ventilator 730 to start operating and control the damper 440 in the valve unit 200 of refrigerant leakage to open in cooperation with the unit controllers 600.

(Advantageous Effect of First Embodiment)

As described above, the air conditioning system 100 according to the first embodiment includes a plurality of the multi branch selectors 300 and has the safety system 700. The safety system 700 includes a plurality of the casings 400 accommodating the multi branch selectors 300, respectively, and each provided with the refrigerant leakage detector 500. The safety system 700 also includes a plurality of individual ducts 710 which function as the connection structure connecting the internal spaces 401 of the casings 400 via the second openings 430 thereof. The safety system 700 further includes the shared duct 720 and the ventilator 730 as the discharge structure connected to the connection structure. The discharge structure is configured to, when an occurrence of the refrigerant leakage has been detected, configured to discharge air from the internal space 401 of the casing 400 in which the refrigerant leakage has occurred.

Thereby, when a refrigerant leakage has occurred in any one of the multi branch selectors 300, the safety system 700 can properly and promptly detect this refrigerant leakage, and discharge the air in the casing 400 covering the multi branch selector to the external space to decrease the concentration of the leaked refrigerant in the internal space 401 of the casing 400. Thus, it is possible to improve safety of the air conditioning system 100 regarding refrigerant leakage in the multi branch selectors 300 which are arranged in separate locations. Moreover, the air in the other casing or casings 400 are not discharged. Hence, the air volume capacity required of the ventilator 730 can be decreased, and thereby the dimension of the ventilator 730 and/or the number of the ventilator 730 can be reduced.

(Modifications of First Embodiment)

In the first embodiment explained above, the unit controllers 600 are serially connected to the central controller 800. However, all or part of the unit controllers 600 may be individually connected to the central controller 800 via individual communication paths. Regarding the individually connected unit controller 600, the central controller 800 can distinguish the unit controller 600 from the other unit controller or controllers 600 by the individual communication path, and transmit the damper open command appropriately just by simply responding to the sender of the leakage signal.

In the first embodiment, a leakage signal indicates the unit ID of the valve unit 200 in which a refrigerant leakage has occurred. Yet, if the unit controller 600 is configured to record transmission of a leakage signal and identify a damper open command as a response to the transmitted leakage signal only when the damper open command has been received within a predetermined time of the transmission, a leakage signal need not necessarily indicate any unit ID. If the central controller 800 and the unit controllers 600 communicate with each other by using different timeslots allocated to the unit controllers 600, a leakage signal need not necessarily indicate any unit ID, either.

Alternatively, the unit controller 600 may control the damper 440 of the own valve unit 200 to open when the unit controller 600 has received detection result information indicating a refrigerant leakage in the own valve unit 200 has occurred. In this case, the central controller 800 need not transmit a damper open command to the unit controller 600. The unit controller 600 may control the damper 440 to open when a predetermined time has lapsed after transmitting the leakage signal, such that the damper 440 opens after the ventilator 730 started operating.

The connection route of the communication path 801 is not limited to the route shown FIG. 3 . For instance, all or part of the unit controllers 600 and the ventilator 730 may be directly connected to the central controller 800 via individual wired/wireless communication paths.

Second Embodiment

(Configuration of Safety System)

In the first embodiment of the present invention mentioned above, the internal spaces 401 of the casings 400 are connected to each other in parallel. On the other hand, in a second embodiment of the present invention explained hereinafter, the internal spaces 401 of the casings 400 are connected to each other in series.

A safety system according to the second embodiment may also be applied to an air conditioning system having the same configuration as the air conditioning system of the first embodiment. The configuration of each of the valve units of the safety system according to the second embodiment may be the same as that of the first embodiment. The same reference signs as the first embodiment are appended to elements and steps which are substantially the same as those of the first embodiment, and the explanations thereof are omitted.

FIG. 6 is a schematic configuration diagram of a safety system according to the second embodiment.

As shown in FIG. 6 , the safety system 700 a of the air conditioning system 100 (see FIG. 1 ) according to the second embodiment comprises the first to third valve units 200_1, 200_2, 200_3, first and second connecting ducts 740 a_1, 740 a_2, a shared duct 720 a, the ventilator 730, and a central controller 800 a. The safety system 700 a does not have the individual ducts 710 of the first embodiment.

The first connecting duct 740 a_1 is connected on one side to the second opening 430_2 of the casing 400_2 of the second valve unit 200_2, and connected on another side to the first opening 420_1 of the casing 400_1 of the first valve unit 200_1. The second connecting duct 740 a_2 is connected on one side to the second opening 430_3 of the casing 400_3 of the third valve unit 2003, and connected on another side to the first opening 420_2 of the casing 400_2 of the second valve unit 200_2.

Hence, the first and second connecting ducts 740 a_1, 740 a_2 form a connection structure which connects the first to third internal spaces 401_1, 401_2, 401_3 via the first openings 4201, 4202 and the second openings 4302, 4303.

To the second opening 430_1 of the casing 400_1 of the first valve unit 200_1, the shared duct 720 a is connected. The ventilator 730 is disposed to the shared duct 720 a at or close to one end (hereinafter referred to as “the second end”) of the shared duct 720, and configured to draw air in the shared duct 720 a towards the second end. It is preferable that the second end of the shared duct 720 a is open to an outdoor space. It is also preferable that the ventilator 730 is disposed at the second end as shown in FIG. 6 . The static pressure capacity of the ventilator 730 of the second embodiment may be different from the ventilator 730 of the first embodiment. To the first opening 420_3 of the third valve unit 200_3, which is the first opening 420 farthest from the ventilator 730 along the air path AP extending over the casings 400 and leading to the ventilator 730, an extension duct may be connected on the outer side of the corresponding casing 400_3.

Hence, the shared duct 720 a and the ventilator 730 form a discharge structure which is connected to the connection structure mentioned above and configured to discharge air from the internal spaces 401 of the casings 400 when all the dampers 440 are open.

The position, the connection to the other elements, and the physical configuration of the central controller 800 a may be the same as those of the central controller 800 according to the first embodiment. Yet, the operation of the central controller 800 a is slightly different from that of the central controller 800 of the first embodiment. The central controller 800 a is configured to control the dampers 440 of all the valve units 200 to be open when the ventilator 730 operates due to an occurrence of the refrigerant leakage.

(Operation of Central Controller)

When an occurrence of the refrigerant leakage in any one of the valve units 200 has been reported, the central controller 800 a is configured to control the ventilator 730 to start operating similarly to the first embodiment. Meanwhile, the central controller 800 a is configured to control the dampers 440 of all the valve units 200 to open.

FIG. 7 is a flow chart indicating an operation performed by the central controller 800 a.

As shown in FIG. 7 , the central controller 800 a performs the same steps as steps S2010 to S2040 of FIG. 5 . Yet, the central controller 800 a perform step S2050 a instead of step S2050 of FIG. 5 .

In step S2050 a, the central controller 800 a transmits a damper open command to all the valve units 200. More specifically, the central controller 800 a transmits a damper open command designating all the valve units 200 including the originator of the leakage signal and serially connected to this originator. The central controller 800 a may make this designation by using the unit IDs of the valve units 200. Then, the central controller 800 terminates its operation. The central controller 800 a may output alarm information and/or control the timing of transmission of the damper open command as mentioned in the first embodiment.

When all the first to third dampers 440_1, 440_2, 440_3 (see FIG. 6 ) are open, an air path AP can be formed that extends from an external space outside the casing 400_3 of the third valve unit 200_3 to the ventilator 730. This air path AP passes through the first opening 420_3, the internal space 401_3, and the second opening 430_3 of the third valve unit 2003, the second connecting duct 740 a_2, the first opening 420_2, the internal space 401_2, and the second opening 430_2 of the second valve unit 200_2, the first connecting duct 740 a_1, the first opening 420_1, the internal space 401_1, and the second opening 430_1 of the first valve unit 200_1, and the shared duct 720 a. If the ventilator 730 operates in this state, the air in the internal spaces 401 of the casings 400 of the first to third valve units 200_1, 200_2, 200_3 are discharged by the suction force of the ventilator 730.

(Advantageous Effect of Second Embodiment)

Accordingly, the air conditioning system 100 according to the second embodiment includes a plurality of the multi branch selectors 300 and has the safety system 700 a. The safety system 700 a includes a plurality of the casings 400 accommodating the multi branch selectors 300, respectively, and each provided with the refrigerant leakage detector 500. The safety system 700 a also includes a plurality of connecting ducts 740 a which function as the connection structure connecting the internal spaces 401 of the casings 400 via the first openings 420 and second openings 430 thereof. The safety system 700 a further includes the shared duct 720 a and the ventilator 730 as the discharge structure connected to the connection structure. The discharge structure is configured to, when an occurrence of the refrigerant leakage has been detected, discharge air from the internal spaces 401 of all the casings 400 including the casing 400 in which the refrigerant leakage has occurred.

Thereby, when a refrigerant leakage has occurred in any one of the multi branch selectors 300, the safety system 700 a can properly and promptly detect this refrigerant leakage, and discharge the air in the casing 400 covering the multi branch selector 300 to the external space to decrease the concentration of the leaked refrigerant in the internal space 401 of the casing 400. Thus, it is possible to improve safety of the air conditioning system regarding refrigerant leakage from valves in the multi branch selectors 300 which are arranged in separate locations. Moreover, it is possible to reduce the total length of ducts for connecting the casings 400 to the ventilator 730 compared with the configuration of the first embodiment, and thereby reduce the installation cost of the system.

(Modifications of Second Embodiment)

In the second embodiment explained above, the ventilator 730 is connected to one of the casings 400 via the shared duct 720 a. Yet, the shared duct 720 a with short length and the ventilator 730 may be integrated as a single element. If one of the casings has a part exposed to the outdoor space, such a single element may be disposed in this part.

In the second embodiment, a leakage signal indicates the originator of leakage signal by the unit ID of the valve unit 200 in which a refrigerant leakage has occurred, and the central controller 800 a identifies the valve unit 200 of refrigerant leakage. Yet, a leakage signal need not necessarily indicate the originator of leakage signal much less the unit ID, and the central controller 800 a need not necessarily identify the valve unit 200 of refrigerant leakage.

The connection route of the communication path 801 is not limited to the route shown FIG. 6 . For instance, all or part of the unit controllers 600 and the ventilator 730 may be directly connected to the central controller 800 a via individual wired/wireless communication paths.

Third Embodiment

As a third embodiment of the present invention, a configuration is explained in which the configurations according to the first and second embodiments are combined. A safety system according to the third embodiment may be applied to an air conditioning system having the same configuration as the air conditioning systems of the first and second embodiments. The configuration of each of valve units of the safety system according to the third embodiment may be the same as that of the first and second embodiments. The same reference signs as the first and second embodiments are used to elements and steps which are substantially the same as those of the first and second embodiments, and the explanations thereof are omitted.

FIG. 8 is a schematic configuration diagram of the safety system according to the third embodiment.

As shown in FIG. 8 , the safety system 700 b of the air conditioning system 100 (see FIG. 1 ) according to the third embodiment comprises the first to third valve units 200_1, 200_2, 200_3, the first and second individual ducts 7101, 7102, the second connecting duct 740 a_2, a shared duct 720 b, the ventilator 730, and a central controller 800 b. The safety system 700 b does not have the third individual duct 710_3 of the first embodiment and the first connecting duct 740 a_1 of the second embodiment.

The first individual duct 710_1 connects the second opening 430_1 of the casing 400_1 of the first valve unit 200_1 to the shared duct 720 b. The second individual duct 710_2 connects the second opening 430_2 of the casing 400_2 of the second valve unit 200_2 to the shared duct 720 b. The second connecting duct 740 a_2 connects the second opening 430_3 of the casing 400_3 of the third valve unit 200_3 to the first opening 4202 of the casing 400_2 of the second valve unit 200_2.

Hence, the first and second individual ducts 7101, 710_2 and the second connecting duct 740 a_2 form a connection structure which connects the first to third internal spaces 401_1, 401_2, 401_3 via the first opening 4202 and the second openings 430_1, 430_2, 430_3.

The ventilator 730 is disposed to the shared duct 720 b at or close to one end (hereinafter referred to as “the second end”) of the shared duct 720 b, and configured to draw air in the shared duct 720 b towards the second end. It is preferable that the ventilator 730 is disposed at the second end as shown in FIG. 8 . The static pressure capacity of the ventilator 730 may be different from the ventilators 730 according to the first and second embodiments.

Hence, the shared duct 720 b and the ventilator 730 form a discharge structure which is connected to the connection structure mentioned above and configured to discharge air from the internal space 401_1 of the casing 400_1 of the first valve unit 200_1 when the damper 440_1 of the first valve unit 200_1 is open, and discharge air from the internal spaces 4012, 401_3 of the casings 400_2, 400_3 of the second and third valve units 200_2, 200_3 when both the dampers 440_2, 440_3 of the second and third valve units 200_2, 200_3 are open.

The position, the connection to the other elements, and the physical configuration of the central controller 800 b may be the same as those of the central controller 800 according to the first embodiment. The central controller 800 b is also configured to perform basically the same operation as the central controller 800 according to the first embodiment. The central controller 800 b controls the damper or dampers 440 of all or part of the valve units 200 to be open when the ventilator 730 operates due to an occurrence of the refrigerant leakage.

Yet, the operation of the central controller 800 b is slightly different from that of the central controllers 800, 800 a according to the first and second embodiments. The central controller 800 b has a grouping table which defines the relationship between each of the valve units 200 and dampers 440 to be opened when a refrigerant leakage has occurred in the valve unit 200. The central controller 800 b is configured to determine the valve unit 200 which should open its damper 440 based on the grouping table.

FIG. 9 is the grouping table used by the central controller 800 b.

As shown in FIG. 9 , the grouping table 910 b associates a destination 912 b of a damper open command with each of the valve units 200 as an originator 911 b of a leakage signal with the valve unit or units 200. The destination 912 b is the valve unit or units 200 in which the damper or dampers 440 should be opened when a refrigerant leakage has occurred in the valve unit 200 as the originator 911 b.

In other words, the grouping table 910 b indicates groups of the valve units 200. In the group including a plurality of the valve units 200, the internal spaces 401 of the casings 400 are connected to the ventilator 730 in series. Between the different groups, the internal spaces 401 of the casings 400 are connected to the ventilator 730 in parallel. The valve units 200 may be defined in the grouping table 910 b by their unit IDs.

For instance, with the unit ID “U1” of the first valve unit 200_1 as the originator 911 b, only the unit ID “U1” of the first valve unit 200_1 as the destination 912 b is associated. With each of the unit IDs “U2” and “U3” of the second and third valve units 200_2, 200_3 as the originator 911 b, the unit IDs “U2” and “U3” of the second and third valve units 200_2, 200_3 as the destination 912 b are associated. The grouping table 910 b is stored in the central controller 800 b in advance. The central controller 800 b may accept a manually setting of the grouping table 910 b.

Yet, the structure of the grouping table 910 b is not limited to that shown in FIG. 9 . For instance, the grouping table 910 b may simply define groups of the valve units 200 such that the valve units 200 connected to the ventilator 730 in series by the connection structure form a group. The single valve unit 200 to which no other valve unit 200 is connected in series with respect to the ventilator 730 by the connection structure may also form a group. Each group may be defined by using identifications of the unit controllers 600.

The central controller 800 b performs substantially the same steps as steps S2010 to S2050 of FIG. 5 . Yet, in step S2030 or S2050, the central controller 800 b determines the valve unit 200 which should open its damper 440 based on the originator 911 b of the received leakage signal and the grouping table 910 b. Thus, when the refrigerant leakage has occurred in the first valve unit 200_1 for instance, the central controller 800 b transmits a damper open command designating the first valve unit 200_1.

Thereby, as depicted in FIG. 8 , only the damper 4401 of the first valve unit 200_1 is opened to create an air path AP passing through the first opening 420_1, internal space 401_1, second opening 430_1 of the first valve unit 200_1, the first individual duct 710_1, and the shared duct 720 b. The dampers 440_2, 440_3 of the second and third valve units 200_2, 200_3 are kept closed. Thus, the ventilator 730 draws air from the internal space 401_1 of the first valve unit 200_1, but not air from the internal spaces 401_2, 4013 of the second and third valve units 200_2, 200_3.

Accordingly, the air conditioning system 100 according to the third embodiment includes the safety system 700 b in which the casings 400 serially connected to each other are further connected to the other casing 400 in parallel. Even with such a connection structure with a complicated configuration, it is possible to discharge air from the internal space 401 of the casing 400 in which the refrigerant leakage has occurred, while reducing static pressure capacity required of the ventilator 730.

The modifications mentioned in the first and second embodiments may be applied to a safety system 700 b according to the third embodiment. It should be noted that the grouping table 910 b and the determination of the valve unit 200 to open its damper 440 based on the grouping table 910 b mentioned above may also be applied to the first and second embodiments.

The connection route of the communication path 801 is not limited to the route shown FIG. 8 . For instance, all or part of the unit controllers 600 and the ventilator 730 may be directly connected to the central controller 800 b via individual wired/wireless communication paths.

Other patterns of combination of the configurations according to the first and second embodiments may also be considerable. For instance, to the first opening 420 of the first valve unit 200, the second openings 430_2, 430_3 of the second and third valve units 200_2, 200_3 may be connected in parallel by a branched duct. In such a configuration, the branched duct functions as both the individual ducts 7102, 710_3 of the first embodiment and the connecting ducts 740 a_1, 740 a_2 of the second embodiment.

In any case, the central controller 800 b is configured to open all the damper or dampers 440 existing on a line which extends from the ventilator 730, passes through the internal space 401 of the casing 400 with refrigerant leakage, and reaches the external space of the casing 400. It is preferable that the central controller 800 b keeps the other damper or dampers closed.

Fourth Embodiment

As a fourth embodiment of the present invention, a configuration is explained in which there are a plurality of sets of the connection structure and the discharge structure. A safety system according to the fourth embodiment may be applied to an air conditioning system having the same configuration as the air conditioning systems of the first to third embodiments. The configuration of each of valve units of the safety system according to the fourth embodiment may be the same as that of the first to third embodiments. The same reference signs as the first to third embodiments are used to elements and steps which are substantially the same as those of the first to third embodiments, and the explanations thereof are omitted.

FIG. 10 is a schematic configuration diagram of the safety system according to the fourth embodiment.

As shown in FIG. 10 , the safety system 700 c of the air conditioning system 100 (see FIG. 1 ) according to the fourth embodiment comprises a first section 701 c_1, a second section 701 c_2, and a central controller 800 c.

The first section 701 c_1 includes the first and second valve units 200_1, 200_2, the first and second individual duct 710_1, 7102, the first shared duct 720_1, and the first ventilator 730_1. Yet, the number of the valve units 200 in each section 701 c is not limited to two, and may be one, three, or more. Similarly to the first embodiment, the first and second valve units 200_1, 200_2 are connected to each other in parallel and commonly connected to the first shared duct 720_1 via the first and second individual duct 710_1, 710_2. The unit controllers (not shown in FIG. 10 , see FIG. 3 ) of the first and second valve units 200_1, 200_2 and the first ventilator 730_1 are connected to the central controller 800 c by the communication path 801.

The second section 701 c_2 includes the third and fourth valve units 200_3, 200_4, the connecting duct 740 a, the second shared duct 7202, and the second ventilator 730_2. Similarly to the second embodiment, the third and fourth valve units 200_3, 200_4 are connected to each other via the connecting duct 740 a and connected to the second shared duct 720_2 in series. The unit controllers (not shown in FIG. 10 , see FIG. 6 ) of the third and fourth valve units 200_3, 200_4 and the second ventilator 730_2 are connected to the central controller 800 c by the communication path 801.

The position, the connection to the other elements, and the physical configuration of the central controller 800 c may be the same as those of the central controller 800 b according to the third embodiment. The central controller 800 c is also configured to perform basically the same operation as the central controller 800 b according to the third embodiment. The central controller 800 c controls the damper or dampers 440 (not shown in FIG. 10 , see FIGS. 3 and 6 ) of all or part of the valve units 200 to be open when the ventilator 730 operates due to an occurrence of the refrigerant leakage. The central controller 800 c determines the valve unit 200 which should open its damper 440 based on the grouping table similarly to the central controller 800 b of the third embodiment.

Yet, the central controller 800 c uses a different type of a grouping table to further determine the ventilator which should start operating. More specifically, the central controller 800 c is configured to control the ventilator of only the section in which a refrigerant leakage has occurred to start operating.

FIG. 11 is a grouping table used by the central controller 800 c.

As shown in FIG. 11 , the grouping table 910 c associates, in addition to the destination or destinations 912 b of a damper open command, a ventilator 913 c which should operate with each of the valve units 200 as an originator 911 b of a leakage signal. In other words, the grouping table 910 c indicates the sections 701 c. In each of the sections, the internal spaces 401 of the valve units 200 (not shown in FIG. 10 , see FIG. 2 ) are connected to the same ventilator, but not connected to the ventilator of the other section. The ventilators may be defined in the grouping table 910 c by their ventilator IDs.

For instance, with the unit ID “U1” of the first valve unit 200_1 as the originator 911 b, the unit ID “U1” of the first valve unit 200_1 as the destination 912 b and a ventilator ID “F1” of the first ventilator 730_1 as the ventilator 913 c to operate are associated. With the unit ID “U2” of the second valve unit 200_2 as the originator 911 b, the unit ID “U2” of the second valve unit 200_2 as the destination 912 b and a ventilator ID “F1” of the first ventilator 730_1 as the ventilator 913 c to operate are associated. With each of the unit ID “U3” of the third valve unit 200_3 and the unit ID “U4” of the fourth valve unit 200_4 as the originator 911 b, the unit IDs “U3” and “U4” of the third and fourth valve units 2003, 200_4 as the destination 912 b and a ventilator ID “F2” of the second ventilator 730_2 as the ventilator 913 c to operate are associated. The grouping table 910 c is stored in the central controller 800 c in advance. The central controller 800 c may accept a manually setting of the grouping table 910 c.

Yet, the structure of the grouping table 910 c is not limited to that shown in FIG. 11 . For instance, the grouping table 910 c may simply define groups of the valve units 200 such that the valve units 200 connected to the same ventilator 730 in series by the connection structure form a group, and associates the group with the corresponding ventilator 730. The single valve unit 200 to which no other valve unit 200 is connected in series with respect to the ventilator 730 by the connection structure may also form a group. Each group may be defined by using identifications of the unit controllers 600.

The central controller 800 c performs substantially the same steps as steps S2010 to S2050 of FIG. 5 . Yet, the central controller 800 c determines in step S2030 or S2040 the ventilator which should start operating based on the originator of the received leakage signal and the grouping table 910 c, and determines in step S2030 or S2050 the valve unit or units 200 each of which should open its damper 440 based on the originator of the received leakage signal and the grouping table 910 c.

Thus, when the refrigerant leakage has occurred in the first valve unit 200_1 for instance, the central controller 800 c transmits a ventilator start command to the first ventilator 730_1 for starting its operation, and transmits a damper open command designating the first valve unit 200_1. As a result, only the first ventilator 730_1 among the ventilators operates, and the damper of only the first valve unit 200_1 among the valve units 200 opens. The ventilator start command may designate the ventilator ID of the ventilator which should start operating.

Accordingly, the air conditioning system 100 according to the fourth embodiment includes the safety system 700 c which is sectioned into a plurality of sections 701 c controlled by the common central controller 800 c. The central controller 800 c is configured to, when a refrigerant leakage in any one of the valve units 200 has occurred, control the ventilator of only the section 701 c in which the refrigerant leakage has occurred to start operating, and control only the damper or dampers 440 which should be opened in order to discharge air from the valve unit 200 of refrigerant leakage. Thereby, the air discharge can be performed appropriately while reducing electricity consumption.

When the valves of the air conditioning system 100 are arranged in widely separated locations, extending ducts from all the valve units 200 to the same common ventilator would result in an increase in the total length of the ducts and static pressure capacity required of the ventilator. Moreover, there might be cases where it is difficult to draw a continuous ducting to cover all the valve units 200 due to limitations imposed by the installation place. In such a case, it is possible to dispose a plurality of the safety system. However, providing the central controller to each of the safety systems would be uneconomical. Hence, by the safety system 700 c according to the fourth embodiment, it is possible to improve safety of the air conditioning system 100 regarding refrigerant leakage from valves at a low cost even if the valves are arranged in widely separated locations.

The connection route of the communication path 801 is not limited to the route shown FIG. 10 . For instance, the third and fourth valve units 200_3, 2004 and the second ventilator 730_2 of the second section 701 c_2 may be connected to the central controller 800 c by another communication path 801 independently from the first section 701 c_1, or indirectly connected to the central controller 800 c via the unit controller or controllers 600 of the first section 701 c_1. All or part of the unit controllers 600 and the ventilators 730 may be directly connected to the central controller 800 c via individual wired/wireless communication paths. The connection routes of the casings 400 of the valve units 200 by ducts are also not limited to the routes shown in FIG. 10 .

(Other Modifications of First to Fourth Embodiments)

The above-mentioned configurations and operations of the safety systems 700, 700 a, 700 b, 700 c may be modified in accordance with circumstances.

For instance, the valve unit 200 may have a configuration including the heatsource-side liquid pipe portion 310, the utilization-side liquid pipe portions 311, the low-pressure gas pipe portion 320, the low-pressure gas sub pipes 321, the high-pressure gas pipe portion 340, the high-pressure gas sub pipes 341, the utilization-side gas pipe portions 330, the low-pressure gas control valves 361, and the high-pressure gas control valves 362, but not including all or part of the sets of the bypass pipe 351, the refrigerant heat exchanger 352, and the expansion mechanism 363. All or part of the gas shut-off valves 365 may be further omitted.

Moreover, the air conditioning system 100 may have a heat pump system with a so-called two-pipe configuration. In such a case, the piping accommodated in the casing 400 would not be the multi branch selector 300. Yet, the valve unit 200 has at least a liquid refrigerant pipe portion, a gas refrigerant pipe portion, a liquid control valve disposed in the liquid refrigerant pipe portion, and a gas control valve disposed in the gas refrigerant pipe portion. Each of the liquid control valve and the gas control valve may be any type of valve for controlling flow of refrigerant in the corresponding pipe portion.

For instance, any one of the safety systems 700, 700 a, 700 b, 700 c may include the valve unit 200 d as shown in FIG. 12 instead of the valve unit 200 of FIG. 2 . Compared with the configuration of FIG. 2 , the valve unit 200 d as a modification of the present embodiment does not necessarily have the high-pressure gas pipe portion 340, the low-pressure gas sub pipes 321, the high-pressure gas sub pipes 341, the bypass pipes 351, the refrigerant heat exchangers 352, the low-pressure gas control valves 361, the high-pressure gas control valves 362, and the expansion mechanisms 363.

Furthermore, any one of the above-mentioned valve units may have a configuration in which the heatsource-side liquid pipe portion 310 and the gas pipe portion or portions 320, 340 are not branched towards two or more of the utilization-side units 120 of the air conditioning system 100 but directed towards only one among the utilization-side units 120. Even in such configurations, each valve disposed in the refrigerant pipe portions within the casing 400 would be a leakage point of refrigerant, and thus the safety regarding refrigerant leakage should be improved.

The casing 400 of any one of the above embodiments and modifications may comprise a plurality of casing parts which are attachable to and detachable from each other. In this case, the casing parts may be structured such that each of the pipe apertures 410 is formed between two or more of the adjoining casing parts. Thereby, each extending pipe can easily be fitted into the corresponding pipe aperture 410 when the casing parts are assembled.

The method for assembling the safety system 700/700 a/700 b/700 c may include steps of: arranging, for each of the valve units 200/200 d, the corresponding casing parts around at least the liquid control valve and the gas control valve of the valve units 200/200 d; fixing, for each of the valve units 200/200 d, the corresponding casing parts to each other; disposing, for each of the valve units 200/200 d, the refrigerant leakage detector 500; arranging the connection structure so as to connect the internal spaces 401 of the casings 400; and connecting the discharge structure to the connection structure or one of the casings 400. Thereby, the casing 400 can be retrofitted to existing valves of a heat pump system. The insulators 450 may also be applied to the gap between the adjoining casing parts.

The unit controller 600 of each valve unit 200 may have further functions. For instance, the unit controller 600 may be further configured to, when a refrigerant leakage in any of the utilization-side piping sections has occurred, control the liquid shut-off valve 364 and the gas shut-off valve 365 (see FIG. 2 ) defining the utilization-side piping section to close. Thereby, the utilization-side piping section can be zoned from other parts of the heat pump circuit. Alternatively, or in addition to this, when a refrigerant leakage has been detected in any one of the valve units 200, the unit controller 600 may shut-down the air conditioning system 100 by, for instance, stopping the operation of the compressor in the heatsource-side unit and the operations of the utilization-side units 120. Thereby, it is possible to prevent as much as possible the refrigerant from leaking out further.

The position, the orientation, and the number of the ventilator 730 are not limited to those according to the first to fourth embodiments. For instance, the ventilator 730 may be arranged so as to blow air towards the internal space 401 of the casing 400 in which a refrigerant leakage has occurred. Thereby, it is also possible to discharge the air containing refrigerant from the corresponding first opening 420 with the damper 440 open. In addition, an additional ventilator may be provided to the individual duct 710, the connecting duct 740 a, and/or the shared duct 720, 720 a between the ventilator 730 and any one of the internal spaces 401 to boost the suction force.

If refrigerant used is heavier than air and thus it is permissible to form the first opening 420 in the upper part of the casing 400, the damper 440 for the first opening 420 is not necessarily required. If the isolation of the internal space 401 of the casing 400 is sufficient without any specific insulators 450, such insulators 450 may be omitted.

All or part of the unit controller 600 may be separated from the corresponding valve unit 200. In this case, the valve unit 200 should have a communication interface such that the unit controller 600 can acquire the detection value Vs of the refrigerant leakage detector 500 and control the operation of the machineries of the valve unit 200 including the damper 440.

All or part of the unit controllers 600 may be integrated to the central controller 800/800 a/800 b/800 c. For instance, the central controller 800/800 a/800 b/800 c may compare the detection values Vs with the detection value threshold Vth. Conversely, all or part of the central controller 800/800 a/800 b/800 c may be integrated to the unit controllers 600. For instance, each of the unit controller 600 may determine whether to open the damper 440 of the own valve unit 200.

If the discharge of the internal air is performed continuously or regularly, under the control of the unit controller 600 for instance, detection of the refrigerant leakage does not necessarily need to be performed, and thus the refrigerant leakage detector 500 is not required. In this case, the operations shown in FIGS. 4, 5, and 7 are not necessarily required. Moreover, if ventilation of the internal air via the connection structure is induced by natural convection or an air flow caused by an external mechanism, the ventilator 730 is not necessarily required.

(Other Variations of Piping in Casing)

As mentioned above, the piping accommodated in the casing 400 is not limited to the multi branch selector 300. For instance, other elements which are potential refrigerant leakage points, such as the compressor of the heatsource-side unit 110, may be accommodated in the casing 400. The casing 400 of the compressor may also be connected to the other casing or casings 400 by the connection structure and provided with the discharge structure in the same manner as the casings 400 of a plurality of the multi branch selectors 300 as explained above.

Fifth Embodiment

(Configuration of Air Conditioning System)

As a fifth embodiment of the present invention, an air conditioning system is explained which can further improve safety regarding a refrigerant leakage from the compressor and its surrounding elements. In the fifth embodiment, a space surrounding a compressor unit is further subjected to the detection of refrigerant leakage and the discharge of air.

The air conditioning system according to the fifth embodiment is similar to the air conditioning system 100 according to the first embodiment. However, the configuration of the safety system is different from that of the first embodiment. The piping configuration may also be different from that of the first embodiment. These differences are explained hereinafter, and the other configurations not referred to are the same as the first embodiment unless otherwise indicated. The same reference signs as the first embodiment are appended to elements which are substantially the same as those of the first embodiment, and the explanations thereof are omitted.

FIG. 13 is a schematic configuration diagram of an air conditioning system according to the fifth embodiment.

As shown in FIG. 13 , the air conditioning system 100 h according to the fifth embodiment has the heatsource-side unit 110 h, the valve unit 200 h, and the utilization-side units 120 which are connected by refrigerant pipes as with the first embodiment. Although being in the two-pipe configuration like the configuration shown in FIG. 12 , the heat pump system of the air conditioning system 100 h may have the three-pipe configuration like the configuration shown in FIG. 1 . In addition, although having the single valve unit 200 h, the air conditioning system 100 h may have two or more valve units 200 h like the configuration shown in FIG. 1 . Meanwhile, as shown in FIG. 13 , the heatsource-side unit 110 h of the present embodiment is separated into two separate units of a HEX unit (a heat exchanger unit) 101 h and a compressor unit 111 h.

The compressor unit 111 h has a compressor 112 h configured to compress first refrigerant. The compressor unit 111 h may further have a switching mechanism 113 h configured to switch the state of the heat pump system between a cooling operation mode and a heating operation mode. In the cooling operation mode, a discharge port of the compressor 112 h is connected to a piping leading to a later-mentioned outdoor heat exchanger, and a suction port of the compressor 112 h is connected to a piping leading to later-mentioned indoor heat exchangers. In the heating operation mode, the discharge port of the compressor 112 h is connected to the piping leading to the later-mentioned indoor heat exchangers, and the suction port of the compressor 112 h is connected to the piping leading to the later-mentioned outdoor heat exchanger. The switching mechanism 113 h is a four-way valve for instance. Yet, the switching mechanism 113 h may be omitted if only either one of the cooling operation mode and the heating operation mode needs to be performed.

The HEX unit 101 h has an outdoor heat exchanger 102 h which is configured to allow air to pass therethrough and allow the first refrigerant to flow therein to exchange heat between the air and the first refrigerant. The outdoor heat exchanger 102 h is connected to one of the discharge port and the suction port of the compressor 112 h via part of the gas refrigerant pipe 132. The outdoor heat exchanger 102 h is also connected to the later-mentioned indoor heat exchangers via the liquid refrigerant pipe 131, the heatsource-side liquid pipe portion 310 and the utilization-side liquid pipe portions 311 of the valve unit 200 h, and the utilization-side liquid refrigerant pipe 151. The outdoor heat exchanger 102 h may be provided with a fan to facilitate flow of the air.

Each of the utilization-side unit 120 has an indoor heat exchanger 122 h which corresponds to the utilization-side heat exchanger mentioned in the first embodiment. Each of the indoor heat exchangers 122 h is connected to the outdoor heat exchanger 102 h via the above-mentioned piping, and configured to allow air to pass therethrough and allow the first refrigerant to flow therein to exchange heat between the air and the first refrigerant. Each of the indoor heat exchangers 122 h is further connected to the other one the discharge port and the suction port of the compressor 112 h via the utilization-side gas refrigerant pipe 152, the utilization-side gas pipe portion 330 and the low-pressure gas pipe portion 320 of the valve unit 200 h, and another part of the gas refrigerant pipe 132. Each of the indoor heat exchangers 122 h may be provided with a fan to facilitate flow of the air.

The air conditioning system 100 h further has expansion mechanisms (not shown), such as electric expansion valves, for decompressing and expanding the first refrigerant flowing between the outdoor heat exchanger 102 h and the indoor heat exchangers 122 h. The air conditioning system 100 h may further has an accumulator (not shown) disposed in the gas refrigerant pipe 132 at a point close to the suction port of the compressor 112 h for accumulating excess refrigerant and separating gas refrigerant from the first refrigerant. The air conditioning system 100 h may further has sensors (not shown) for detecting temperature and/or pressure of refrigerant which are necessary for controlling the operation of the air conditioning system 100 h.

Thus, the air conditioning system 100 h has first connection pipes connecting the HEX unit 101 h and the compressor unit 111 h such that the first refrigerant circulates therebetween, and second connection pipes connecting the compressor unit 111 h, the valve unit 200 h, and the utilization-side units 120 such that the first refrigerant circulates between the compressor unit 111 h and the utilization-side units 120 via the valve unit 200 h. In other words, the HEX unit 101 h, the compressor unit 111 h, the valve unit 200 h, and each of the utilization-side units 120 are connected via refrigerant pipes so as to form a heat pump circuit using the first refrigerant.

Here, the “first refrigerant” may be CO2 refrigerant (carbon oxide refrigerant), R290 refrigerant (propane), HFC refrigerant such as R32 and R410A, or HFO refrigerant such as R-1234ze and R-1234yf, but is not limited to these refrigerants.

In this embodiment, the HEX unit 101 h is installed in a first space 931 h which is an outdoor space or a space through which outdoor air is allowed to pass. Thereby, the outdoor heat exchanger 102 h can be continuously supplied with drafts of outdoor air to effectively release heat from or absorb heat into the first refrigerant. The utilization-side units 120 are installed in a target space 933 h which is to be air conditioned. Thereby, the indoor heat exchangers 122 h can perform a heat exchange between the first refrigerant and air in the target space 933 h to cool or warm it. Yet, the utilization-side units 120 need not necessarily be installed in the target space 933 h. If an outlet port of each of the utilization-side units 120 for supplying air-conditioned air leads to the target space 933 h via a duct or the like, the utilization-side units 120 may be disposed outside the target space 933 h.

Meanwhile, the compressor unit 111 h and the valve unit 200 h are installed in a second space 932 h which is different from any of the first space 931 h and the target space 933. As detailed later, it is preferable that the second space 932 h is substantially isolated in normal times from at least the first space 931 h and the target space 933 h, and ventilation of the second space 932 h is controlled independently from that of the first space 931 h and the target space 933 h.

For instance, the target space 933 is a room of a building to which the air conditioning system 100 h is installed such as an office room. Thus, the utilization-side units 120 are so-called indoor units. The first space 931 h is a room of the same building which has an air passage or passages freely leading to the outdoor space, or an outdoor space outside the building such as a space of a roof floor of the building. The second space 932 h is another room of the same building such as a machine room, a computer room, or a warehouse.

(Configuration of Safety System)

The safety system of the present embodiment includes a ventilation control structure for controlling the ventilation environment of the second space 932 h. In this embodiment, a configuration is explained in which the ventilation control structure causes a forced ventilation of the second space 932 h when a refrigerant leakage has occurred in the second space 932 h. More specifically, the ventilation control structure includes a discharge structure that operates to discharge air from the second space 932 h when concentration of the first refrigerant in the second space 932 h has increased.

FIG. 14 is a schematic configuration diagram of the safety system of the air conditioning system 100 h.

As shown in FIG. 14 , the second space 932 h is defined as a room by a building structure 934 h. In other words, the internal space of the building structure 934 h is the second space 932 h. This building structure 934 h may also be regarded as part of the ventilation control structure.

For instance, the building structure 934 h includes a floor, a ceiling facing the floor, and at least one wall which connects the floor and the ceiling and surrounds a space between the floor and a ceiling. The building structure 934 h may further include a door arranged in the floor, the ceiling, or the wall. The building structure 934 h is formed with a first airflow passage 935 h and a second airflow passage 936 h between the second space 932 h and an outer space outside of the second space 932 h. This outer space is preferably the outdoor space.

The safety system 700 h includes a refrigerant leakage detector (a first leakage detector) 500 disposed in the second space 932 h, and a discharge structure. The discharge structure includes a damper 440 disposed to the first airflow passage 935 h, a ventilator 730 disposed to the second airflow passage 936 h, and a central controller 800 h. Here, any of the refrigerant leakage detector 500 and the central controller 800 h may be part of the compressor unit 111 h or the valve unit 200 h. The configurations of the ventilator 730, the damper 440, and the refrigerant leakage detector 500 may be the same as those of the first to fourth embodiments. As with these embodiments, the ventilator 730, the damper 440, and the refrigerant leakage detector 500 are connected to the central controller 800 h via a communication path 801 by means of a wired and/or wireless communication.

The refrigerant leakage detector 500 is configured to detect at least a concentration of the first refrigerant in air. The ventilator 730 is configured to draw air from the second space 932 h towards an external space which is different from any of the target space 933 h and the second space 932 h via the second airflow passage 936 h. The damper 440 may be a check air damper, and configured to keep the first airflow passage 935 h closed in normal times. Yet, under the control of the central controller 800 h as mentioned later, the damper 440 is configured to open the first airflow passage 935 h when the ventilator 730 is in operation. Thus, the first airflow passage 935 h works as an intake port of an external air for promoting the ventilation of the second space 932 h.

It is noted that any of the first airflow passage 935 h and the second airflow passage 936 h may be an opening formed in the building structure 934 h, or a duct, a pipe, or the like which is connected to such an opening. Thus, the ventilator 730 and/or the damper 440 may be disposed to the building structure 934 h, inside the second space 932 h, or outside the second space 932 h. Such an opening may be formed in any part of the building structure 934 h, such as the wall, the ceiling, the floor, the door, and the window. For instance, each of the first airflow passage 935 h and the second airflow passage 936 h is formed in an exterior wall of the building which also defines the second space 932 h. In any cases, it is preferable that the building structure 934 h is configured such that its internal space (i.e. second space 932 h) is substantially closed in the normal times.

The central controller 800 h is configured to, when the detected concentration of the first refrigerant is equal to or greater than a first detection value threshold (e.g. when the detected concentration has reached to the first detection value threshold), control the ventilator 730 to operate, and also control the damper 440 to open.

(Operation of Central Controller)

The central controller 800 h corresponds to the central controller 800 of the first embodiment and may have the same hardware configuration as the central controller 800. The central controller 800 h performs an operation similar to the operations by the unit controller 600 and the central controller 800 of the first embodiment. Yet, in the present embodiment, the operation is made simpler.

FIG. 15 is a flow chart indicating the operation performed by the central controller 800 h. In the flow chart, steps S3010 h, S3020 h, S3030 h, S3040 h, and S3050 h correspond to steps S1010, S1020, S2040, S1120, S1110 explained in the first embodiment, respectively.

In step S3010 h, the central controller 800 h acquires the detection value as a first detection value Vs1 from the detector signal outputted from the refrigerant leakage detector 500. The central controller 800 h may passively receive the detector signal which is continuously or regularly outputted from the refrigerant leakage detector 500, or actively request the refrigerant leakage detector 500 to output the detector signal regularly.

In step S3020 h, the central controller 800 h compares the first detection value Vs1 acquired and the first detection value threshold Vth1, and determines whether the first detection value Vs1 is less than the first detection value threshold Vth1. The central controller 800 h may obtain a moving average value of the detection values Vs1 in a certain time length to use the moving average value as the first detection value Vs1 which is compared with the first detection value threshold Vth1.

The first detection value threshold Vth1 is stored in the central controller 800 h in advance. The first detection value threshold Vth1 may be a value determined by experiments or the like such that false detections and detection omissions of refrigerant leakages are avoided as much as possible. It is preferable that the first detection value threshold Vth1 is set to a value less than a value corresponding to 25% of the Lower Flammability Limit (LFL) of the refrigerant used.

If the first detection value Vs1 is equal to or greater than the first detection value threshold Vth1 (S3020 h: No), the central controller 800 h proceeds to later-mentioned step S3030 h. If the first detection value Vs1 is less than the first detection value threshold Vth1 (S3020 h: Yes), the central controller 800 h proceeds to later-mentioned step S3050 h.

In step S3030 h, the central controller 800 h transmits a ventilator start command to the ventilator 730 to control the ventilator 730 to start operating. The central controller 800 h may control the operation of the ventilator 730 by controlling a supply of electricity thereto.

In step S3040 h, the central controller 800 h controls the damper 440 to open. For instance, the central controller 800 h controls the state of the damper 440 by controlling a supply of electricity thereto. The central controller 800 h may output alarm information by means of a sound, a light, a visual image, and/or a communication signal from a loudspeaker, an electric light, a display device, and/or a communication interface provided to the central controller 800 h.

The execution order of step S3030 h and step S3040 h may be reversed. Moreover, the damper 440 and the ventilator 730 need not necessarily be controlled directly by the central controller 800 h. The damper 440 may be controlled via the ventilator 730, or the ventilator 730 may be controlled via the damper 440.

In step S3050 h, the central controller 800 h determines whether termination of operation has been designated. The designation may be made by a user operation, another device, or the central controller 800 h itself. If termination of the operation has not been designated (S3050 h: No), the central controller 800 h goes back to step S3010 h to repeat the above acquisition and determination steps. If termination of the operation has been designated (S3050 h: Yes), the central controller 800 h terminates its operation regarding the safety system.

By this operation, when the refrigerant leakage has occurred in any of the compressor unit 111 h and the valve unit 200 h, the state of the second space 932 h can be switched from a normal state (a first state) to an emergency state (a second state) in which a ventilation of the second space 932 h is promoted more than in the normal state.

(Advantageous Effect of Fifth Embodiment)

According to the fifth embodiment mentioned above, differently from the first space 931 h which requires a continuous supply of outdoor air, the ventilation of the second space 932 h can be restricted in normal times. Thereby, when a refrigerant leakage in any of the compressor unit 111 h and the valve unit 200 h has occurred, it is possible to swiftly detect it by the refrigerant leakage detector 500. Then, when the occurrence of refrigerant leakage has been detected, the ventilation of the second space 932 h is started. Hence, the air containing the leaked refrigerant can be discharged from the second space 932 h at an early stage. Accordingly, it is possible to improve safety regarding refrigerant leakage at low cost, even in a case where the compressor 112 h should be arranged inside the building.

Any of the compressor unit 111 h and the valve unit 200 h need not necessarily have a casing like the casings 400 according to the first to fourth embodiments. Yet, it is also possible to apply the safety systems including the casings 400 of any of the first to fourth embodiments to the compressor unit 111 h and the valve unit 200 h of the present embodiment. As variations of the first embodiment, the cases are explained below where the compressor unit 111 h and the valve unit 200 h are covered by one or more casings.

(First Variation of Fifth Embodiment)

In the same manner as the second embodiment (see FIG. 16 ) for two valve units 200, the compressor unit 111 h and the valve unit 200 h may be covered by two casings which are connected in series by the connection structure and provided with the discharge structure.

FIG. 16 is a schematic configuration diagram of a safety system according to a first variation of the fifth embodiment.

As shown in FIG. 16 , a safety system 700 i according to the first variation comprises a compressor unit casing 400_c (a first casing) and a valve unit casing 400_v (a second casing) which are arranged within the second space 932 h as part of the second space 932 h. The compressor unit casing 400_c accommodates at least part of the compressor unit 111 h. This accommodated part includes at least the compressor 112 h. The valve unit casing 400_v accommodates at least part of the valve unit 200 h. This accommodated part includes at least the liquid shut-off valves 364 and the gas shut-off valves 365. The compressor unit casing 400_c may be regarded as part of the compressor unit 111 h, and the valve unit casing 400_v may be regarded as part of the valve unit 200 h.

The compressor unit casing 400_c and the valve unit casing 400_v correspond to the casings 400 according to the second embodiment, and may have the same configurations thereof. The compressor unit casing 400_c is formed with a first opening 420_c and a second opening 430_c, and the valve unit casing 400_v is formed with a first opening 420_v and a second opening 430_v.

The safety system 700 i has a serial structure similar to the second embodiment. The safety system 700 i has a connecting duct 740 which is connected on one side to the second opening 430_c of compressor unit casing 400_c, and connected on another side to the first opening 420_v of the valve unit casing 400_v. Thus, the connecting duct 740 is a connection structure connecting an internal space 401_c of the compressor unit casing 400_c and an internal space 401_v of the valve unit casing 400 v.

The safety system 700 i further has an intake duct 750 i which is connected on one side to the first airflow passage 935 h, and connected on another side to the first opening 420_c of the compressor unit casing 400_c. Thus, the intake duct 750 i connects the outer space of the second space 932 h and the internal space 401_c of the compressor unit casing 400_c. Here, the first airflow passage 935 h may be regarded as part of the intake duct 750 i, or the intake duct 750 i may be regarded as part of the first airflow passage 935 h.

The safety system 700 i further has a shared duct 720 a which is connected on one side to the second opening 430_v of the valve unit casing 400_v, and connected on another side to the second airflow passage 936 h. Thus, the shared duct 720 a is a discharge duct connecting the outer space of the second space 932 h and the internal space 401_v of the valve unit casing 400_v. Here, the second airflow passage 936 h may be regarded as part of the shared duct 720 a, and the shared duct 720 a may be regarded as part of the second airflow passage 936 h.

The safety system 700 i also has a ventilator 730 disposed to the shared duct 720 a. The configurations of these may be the same as those of the shared duct 720 a and the ventilator 730 according to the second embodiment. As already mentioned, any of the first airflow passage 935 h and the second airflow passage 936 h may be an opening of the building structure 934 h or a duct connected to such an opening. Thus, the ventilator 730 and/or the damper 440 may be mounted to the building structure 934 h, arranged inside the second space 932 h, or arranged outside the second space 932 h.

Hence, as with the second embodiment, the compressor unit casing 400_c and the valve unit casing 400_v are connected by the connecting duct 740 in series with respect to the shared duct 720. Yet, differently from the second embodiment, the damper 440 disposed between the compressor unit casing 400_c and the valve unit casing 400_v is omitted. It is noted that the positions of the casing 400_c, 400_v with respect to the intake duct 750 i and the shared duct 720 a may be reversed.

The safety system 700 i further has a compressor unit leakage detector 500_c which corresponds to the refrigerant leakage detector 500 according to the second embodiment. The compressor unit leakage detector 500_c is disposed in the internal space 401_c of the compressor unit casing 400_c, and may be part of the compressor unit 111 h. The compressor unit leakage detector 500_c is configured to detect at least a concentration of the first refrigerant in air.

The safety system 700 i further has a central controller 800 i which corresponds to the unit controller 600 and the central controller 800 a according to the second embodiment, and may have the same hardware configuration as the unit controller 600 and/or the central controller 800 a. The central controller 800 i may be part of the compressor unit 111 h. The central controller 800 i may perform the operation as shown in FIG. 15 based on the detector signal outputted from the compressor unit leakage detector 500_c.

Additionally, as shown in FIG. 16 , the safety system 700 i may further have a valve unit leakage detector 500_v disposed in the internal space 401_c of the valve unit casing 400_v, which may have the same configuration as the compressor unit leakage detector 500_c. In this case, it is preferable that the central controller 800 i further performs the determination of step S3020 h based on the detector signal outputted from the valve unit leakage detector 500_v. In other words, the central controller 800 i starts the ventilator 730 and open the damper 440 when a refrigerant leakage has occurred in any of the compressor unit casing 400_c and the valve unit casing 400_v. The detector signal of the valve unit leakage detector 500_v may be relayed to the central controller 800 i by the unit controller 600 of the valve unit 200 h via the communication path 801, or directly transmitted to the central controller 800 i via the communication path 801.

The total volume of the internal spaces 401_c, 401_v of the casings 400_c, 400_v and internal spaces of the ducts 750 i, 740 a, 720 a between the damper 440 and the ventilator 730 can be made much smaller than the volume of the whole second space 932 h. Thus, both the detection of the refrigerant leakage and the discharge of the air containing the leaked refrigerant can be performed more swiftly compared with the configuration shown in FIG. 14 . Moreover, the casings 400_c, 400_v and ducts 750 i, 740 a, 720 a can prevent or restrain refrigerant leaked from the compressor unit 111 h or the valve unit 200 h from spreading in the second space 932 h. Hence, the safety regarding refrigerant leakage can be further improved.

It is noted that the internal space 401_c of the compressor unit casing 400_c and the internal space 401_v of the valve unit casing 400_v are part of the second space 932 h but can also be regarded as a second space in which the compressor unit 111 h, the valve unit 200 h, and the compressor unit leakage detector 500_c are installed and which is different from any of the target space 933 h and the first space 931 h. In this case, since the internal spaces 401_c, 401_v are substantially closed in normal times, the building structure 934 h need not necessarily be configured to close its internal space (i.e. second space 932 h).

(Second Variation of Fifth Embodiment)

Instead of being connected in series, the casings 400_c, 400_v may be connected in parallel with respect to the shared duct.

FIG. 17 is a schematic configuration diagram of a safety system of an air conditioning system according to a second variation of the fifth embodiment.

The safety system 700 j according to the second variation has the same configuration as the safety system 700 i of the first variation except for the structure for connecting the internal spaces 401_c, 401_v of the casings 400_c, 400_v to the external space or spaces of the second space 932 h. In other words, the casings 400_c, 400_v of the compressor unit 111 h and the valve unit 200 h are connected in the same manner as the casings 400 of the valve units 200 according to the first embodiment as shown in FIG. 3 .

As shown FIG. 17 , the safety system 700 j has a first intake duct 750 i_c which corresponds to the intake duct 750 i according to the first variation. Yet, instead of the connecting duct 740 a and the shared duct 720 a of the first variation, the safety system 700 j has a second intake duct 750 i_v, a first individual duct 710_1, a second individual duct 710_2, and a shared duct 720 b.

The building structure 934 h is further formed with a third airflow passage 937 j between the second space 932 h and an outer space outside of the second space 932 h. The second intake duct 750 i_v is connected on one side to this third airflow passage 937 j, and connected on another side to the first opening 420_v of the valve unit casing 400_v. In other words, the second intake duct 750 i_v connects the outer space of the second space 932 h and the internal space 401_v of the valve unit casing 400_v. Here, the third airflow passage 937 j may be regarded as part of the second intake duct 750 i_v, and the second intake duct 750 i_v may be regarded as part of the third airflow passage 937 j.

The configurations and/or arrangements of the third airflow passage 937 j and the second intake duct 750 i_v may be the same as or similar to those of the first airflow passage 935 h and the first intake duct 750 i_c. A damper 440 is also disposed to the third airflow passage 937 j as with the first airflow passage 935 h. The third airflow passage 937 j may be an opening of the building structure 934 h or a duct connected to such an opening as with the first airflow passage 935 h and the second airflow passage 936 h. Thus, the dampers 440 disposed to the third airflow passage 937 j may also be mounted to the building structure 934 h, arranged inside the second space 932 h, or arranged outside the second space 932 h.

The first individual duct 710_1 connects the second opening 430_v of the valve unit casing 400_v to the shared duct 720 b. The second individual duct 710_2 connects the second opening 430_c of the compressor unit casing 400_c to the shared duct 720 b. Thus, the first and second individual ducts 710_1, 710_2 form a connection structure connecting the internal spaces 401_c, 401_v of the casings 400_c, 400_v, and the shared duct 720 b connects this connection structure and the external space of the second space 932 h. The ventilator 730 is disposed to the shared duct 720 b at or close to one end of the shared duct 720 b, and configured to draw air in the shared duct 720 b towards the second end. The configurations of these elements may be the same as those of the individual ducts 710, the shared duct 720 b, and the ventilator 730 according to the first embodiment.

The central 800 i may perform the operation as shown in FIG. 15 , while controlling both the dampers 440 to open in step S3040 h upon controlling the ventilator 730 to start operating.

With the second variation as explained above, each of the internal spaces 401_c, 401_v communicates with the discharge structure without being interposed by any other casing. Hence, it is possible to reduce static pressure capacity required of the ventilator 730. This would further reduce the installation cost of the air conditioning system. It is noted that the first airflow passage 935 h and the third airflow passage 937 j may be integrated to a single airflow passage. In this case, the dampers 440 for them may also be integrated a single damper.

(Third Variation of Fifth Embodiment)

Instead of being covered by respective casings, the compressor unit 111 h and the valve unit 200 h may be covered by a single casing.

FIG. 18 is a schematic configuration diagram of a safety system of an air conditioning system according to a third variation of a fifth embodiment.

The safety system 700 k according to the third variation has the same configuration as the safety system 700 i of the first variation except for the structure for covering compressor unit 111 h and the valve unit 200 h. As shown in FIG. 18 , the safety system 700 k has a casing 400 arranged within the second space 932 h, instead of the casings 400_c, 400_v and the connecting duct 740 a of the first variation, as part of the second space 932 h. The casing 400 accommodates at least part of the compressor unit 111 h and at least part of the valve unit 200 h. These accommodated parts include at least the compressor 112 h, the liquid shut-off valves 364, and the gas shut-off valves 365. The casing 400 corresponds to each casing 400 according to the second embodiment, and may have the same configuration thereof.

The safety system 700 k also has a refrigerant leakage detector 500 and a central controller 800 i which correspond to the compressor unit leakage detector 500_c and the central controller 800 i according to the first variation, respectively. The refrigerant leakage detector 500 is disposed in an internal space 401 of the casing 400. The central controller 800 i may perform the operation as shown in FIG. 15 based on the detector signal outputted from the refrigerant leakage detector 500.

It is noted that the internal space 401 of the casing 400 is part of the second space 932 h but can also be regarded as a second space in which the compressor unit 111 h, the valve unit 200 h, and the refrigerant leakage detector 500 are installed and which is different from any of the target space 933 h and the first space 931 h. In this case, since the internal space 401 is substantially closed in normal times, the building structure 934 h need not necessarily be configured to close its internal space (i.e. second space 932 h).

This third variation is suitable for the case where the compressor unit 111 h and the valve unit 200 h are arranged close to each other. With this variation, since the number of the casing 400 is decreased and the connecting duct 740 a is not required, it is possible to further reduce the installation cost of the air conditioning system.

Sixth Embodiment

(Configuration of Air Conditioning System)

In the above fifth embodiment, the air conditioning system is configured such that the same refrigerant flows through the HEX unit, the compressor unit, the valve unit, and the utilization units. Yet, the configurations of the safety systems (the ventilation control structures) according to the fifth embodiment and its variations may also be applied to other types of piping. For instance, the safety system can be applied to an air conditioning system of a cascade-type in which two or more circuits of the same or different heat mediums are formed and a heat exchange therebetween is performed. As a sixth embodiment of the present invention, an air conditioning system of a cascade-type is explained.

The air conditioning system according to the sixth embodiment is similar to the air conditioning system 100 h according to the fifth embodiment. Yet, the configuration of the piping is different from that of the fifth embodiment. This difference is explained hereinafter, and the other configurations not referred to are the same as the fifth embodiment unless otherwise indicated. The same reference signs as the fifth embodiment are appended to elements which are substantially the same as those of the fifth embodiment, and the explanations thereof are omitted.

FIG. 19 is a schematic configuration diagram of the air conditioning system according to the sixth embodiment.

As shown in FIG. 19 , the piping of the air conditioning system 100 m according to the sixth embodiment is separated into a first circuit 105 m for first refrigerant and a second circuit 106 m for second refrigerant. The air conditioning system 100 m has a HEX unit 101 m, a compressor unit 111 m, a valve unit 200 m, and utilization-side units 120 m which correspond to the HEX unit 101 h, the compressor unit 111 h, the valve unit 200 h, and the utilization-side units 120 according to the fifth embodiment, respectively.

The HEX unit 101 m includes an outdoor heat exchanger 102 m corresponding to the outdoor heat exchanger 102 h of the fifth embodiment, and the compressor unit 111 m includes a compressor 112 m and a switching mechanism 113 m corresponding to the compressor 112 h and the switching mechanism 113 h of the fifth embodiment. Yet, the compressor unit 111 m according to the present embodiment further has a refrigerant heat exchanger 114 m. The HEX unit 101 m and the compressor unit 111 m are connected by a unit liquid refrigerant pipe 103 m and a unit gas refrigerant pipe 104 m (first connection pipes) such that the first refrigerant circulates therebetween.

The refrigerant heat exchanger 114 m is configured to allow each of the first refrigerant and the second refrigerant to flow therein so as to exchange heat between the first refrigerant and the second refrigerant.

Hence, the compressor 112 m, the switching mechanism 113, the outdoor heat exchanger 102 h, the refrigerant heat exchanger 114 m, and the pipes connecting them form the first circuit 105 m which circulates the first refrigerant.

The valve unit 200 m includes a heatsource-side liquid pipe portion 310 m, a low-pressure gas pipe portion 320 m, utilization-side liquid pipe portions 311 m, utilization-side gas pipe portions 330 m, liquid shut-off valves 364 m, and gas shut-off valves 365 m which correspond to the heatsource-side liquid pipe portion 310, the low-pressure gas pipe portion 320, the utilization-side liquid pipe portions 311, the utilization-side gas pipe portions 330, the liquid shut-off valves 364, and the gas shut-off valves 365 according to the fifth embodiment, respectively. Each of the utilization-side units 120 m includes an indoor heat exchanger 122 m corresponding to the indoor heat exchanger 122 according to the fifth embodiment. The compressor unit 111 m, the valve unit 200 m, and the utilization-side units 120 m are connected to each other via a liquid refrigerant pipe 131 m, a gas refrigerant pipe 132 m, utilization-side liquid refrigerant pipes 151 m, and utilization-side gas refrigerant pipes 152 m corresponding to the liquid refrigerant pipe 131, the gas refrigerant pipe 132, the utilization-side liquid refrigerant pipes 151, and the utilization-side gas refrigerant pipes 152 according to the fifth embodiment.

Yet, differently from the fifth embodiment, these elements of the valve unit 200 m and the utilization-side units 120 m and the refrigerant pipes 131 m, 132 m are configured to allow the second refrigerant to flow therein instead of the first refrigerant.

The liquid refrigerant pipe 131 m and the gas refrigerant pipe 132 m (second connection pipes) are connected to the refrigerant heat exchanger 114 m of the compressor unit 111 m such that the second refrigerant circulates between the compressor unit 111 m and the utilization-side units 120 m via the valve unit 200 m. The air conditioning system 100 m further has a pump 116 m disposed to the liquid refrigerant pipe 131 m or the gas refrigerant pipe 132 m, preferably as part of the compressor unit 111 m. The pump 116 m is configured to induce a flow of the second refrigerant. Hence, the pump 116 m, the indoor heat exchangers 122 m, the refrigerant heat exchanger 114 m, and the pipes connecting them form the second circuit 106 m which circulates the second refrigerant. The pump 116 m may be a compressor for compressing the second refrigerant. In this case, elements required for forming a heat pump circuit such as an expansion mechanism and an accumulator may also be provided to the second circuit 106 m.

Here, the refrigerant type of the second refrigerant is the same as or different from that of the first refrigerant. The “second refrigerant” may be CO2 refrigerant (carbon oxide refrigerant), R290 refrigerant (propane), HFC refrigerant such as R32 and R410A, or HFO refrigerant such as R-1234ze and R-1234yf, but is not limited to these refrigerants. For instance, HFC or HFC refrigerant is used as the first refrigerant, and CO2 refrigerant is used as the second refrigerant.

The HEX unit 101 m is installed in the first space 931 h, the compressor unit 111 m and the valve unit 200 m are installed in the second space 932 h, and the utilization-side units 120 are installed in the target space 933 h. Any of the safety systems 700 h 700 i, 700 j, 700 k according to the first embodiment and its variations may be applied to the air conditioning system 100 m. Nevertheless, in a case where the refrigerant type of the second refrigerant is different from that of the first refrigerant, it is preferable to use a refrigerant leakage detector for the second refrigerant in addition to the refrigerant leakage detector 500 for the first refrigerant.

FIG. 20 is a schematic configuration diagram of an example of a safety system of the air conditioning system 100 m.

As shown in FIG. 20 , a safety system 700 m of the air conditioning system 100 m may have substantially the same configuration as the safety system 700 h of the fifth embodiment. Yet, instead of the refrigerant leakage detector 500 and the central controller 800 h of the fifth embodiment, the safety system 700 m has a first leakage detector 501 m, a second leakage detector 502 m, and a central controller 800 m. The first leakage detector 501 m may be the same as the refrigerant leakage detectors 500_c according to the first variation of the fifth embodiment. The compressor unit 111 m and the valve unit 200 m may be covered by respective casings or a single casing. If the compressor unit 111 m has a casing accommodating at least the compressor 112 m, the first leakage detector 501 m may be disposed in the casing like the first variation of the fifth embodiment.

Meanwhile, the second leakage detector 502 m is disposed in the second space 932 h but outside any casings of the compressor unit 111 m and the valve unit 200 m for instance. The second leakage detector 502 m is configured to detect at least a concentration of the second refrigerant in an air surrounding the second leakage detector 502 m, and continuously or regularly output a detector signal indicating a detection value Vs2 to the central controller 800 m via the communication path 801. The second leakage detector 502 m may be a semi-conductor gas sensor reactive to the second refrigerant. In a case where the second refrigerant is heavier than atmospheric air, such as CO2 refrigerant, the second leakage detector 502 m is preferably disposed in the second space 932 h at or close to an inner bottom surface of the second space 932 h.

The central controller 800 m corresponds to the central controller 800 i of the first variation of the fifth embodiment, and may have the same hardware configuration as the central controller 800 i. Yet, the central controller 800 m according to the present embodiment further controls the ventilator 730 to start operating when the detected concentration of the second refrigerant has been increased.

FIG. 21 is a flow chart indicating an operation performed by the central controller 800 m.

As shown in FIG. 21 , the central controller 800 m performs all steps S3010 h, S3020 h, S3030 h, S3040 h, and S3050 h according to the fifth embodiment shown in FIG. 15 as with the central controller 800 i of the first variation of the fifth embodiment. The central controller 800 m further performs operations of steps S3021 m, S3022 m before step S3010 h or between step S3020 h and step S3050 h.

In step S3021 m, the central controller 800 m acquires the detection value as a second detection value Vs2 from the detector signal outputted from the second leakage detector 502 m. The central controller 800 m may passively receive the detector signal which is continuously or regularly outputted from the second leakage detector 502 m, or actively request the second leakage detector 502 m to output the detector signal regularly. The obtained first detection value Vs2 basically reflects the variation in the concentration of the second refrigerant in the second space 932 h.

In step S3022 m, the central controller 800 m compares the second detection value Vs2 acquired and a second detection value threshold Vth2, and determines whether the second detection value Vs2 is less than the second detection value threshold Vth2. The central controller 800 m may obtain a moving average value of the detection values Vs2 in a certain time length to use the moving average value as the second detection value Vs2 which is compared with the second detection value threshold Vth2.

The second detection value threshold Vth2 is stored in the central controller 800 m in advance. The second detection value threshold Vth2 may be a value determined by experiments or the like such that false detections and detection omissions of refrigerant leakages are avoided as much as possible. It is preferable that the second detection value threshold Vth2 is set to a value less than a value corresponding to 25% of the Lower Flammability Limit (LFL) of the second refrigerant. Also, in case of using a toxic refrigerant such as CO2 refrigerant, as the second refrigerant, it is preferable that the second detection value threshold Vth2 is set to a value less than a value corresponding to the toxicity limit. In case of CO2 refrigerant, the value of the toxicity limit is 0.1 kg/m³. The second detection value threshold Vth2 may be the same as or different from the first detection value threshold Vth1.

If the second detection value Vs2 is equal to or greater than the second detection value threshold Vth2 (S3022 m: No), the central controller 800 m proceeds to step S3030 h. If the second detection value Vs2 is less than the second detection value threshold Vth2 (3022 m: Yes), the central controller 800 m proceeds to step S3050 h.

With the above configuration, when the refrigerant leakage has occurred in any of the compressor unit 111 m and the valve unit 200 m, the ventilation of the second space 932 h can be swiftly performed. Moreover, the second leakage detector 502 m is disposed outside any casings of the compressor unit 111 m and the valve unit 200 m. Thus, even a refrigerant leakage from pipe portions outside the casing or casings covering the compressor unit 111 m and/or the valve unit 200 m, such as the utilization-side liquid refrigerant pipes 151 m or utilization-side gas refrigerant pipes 152 m (in particular the connection parts of the pipes), can be detected. Hence, it is possible to effectively improve the safety of the air conditioning system of a cascade-type regarding refrigerant leakage.

However, the positions of the first and second leakage detectors 501 m, 502 m are not limited to those explained above. For instance, the second leakage detector 502 m may be disposed in a casing of the valve unit 200 m.

The safety system 700 m explained above is preferred for the cascade-type system where HFC refrigerant such as R32 and R410A, or HFO refrigerant such as R-1234ze and R-1234yf is used as the first refrigerant, and C02 refrigerant (carbon oxide refrigerant) as the second refrigerant, for instance.

Seventh Embodiment

(Configuration of Air Conditioning System)

In the above fifth and sixth embodiments, the air conditioning systems are of an air-cooling type in which the first refrigerant is subjected to heat exchange with outdoor air. Yet, the safety systems explained in the fifth and sixth embodiments can also be applied to any other types including a water-cooling type in which the first refrigerant is subjected to heat exchange with coolant water or brine. As a seventh embodiment of the present invention, an air conditioning system of a water-cooling type is explained.

The air conditioning system according to the seventh embodiment is similar to the air conditioning system 100 according to the fifth embodiment. However, the configuration of the piping is different from that of the fifth embodiment. This difference is explained hereinafter, and the other configurations not referred to are the same as the fifth embodiment unless otherwise indicated. The same reference signs as the fifth embodiment are appended to elements which are substantially the same as those of the fifth embodiment, and the explanations thereof are omitted.

FIG. 22 is a schematic configuration diagram of the air conditioning system according to the seventh embodiment.

As shown in FIG. 22 , the piping of the air conditioning system 100 n according to the seventh embodiment is separated into a first circuit 105 n for heat medium and a second circuit 106 n for first refrigerant. The heat medium may be coolant water or brine. The air conditioning system 100 n has a HEX unit 101 n, a compressor unit 111 n, a valve unit 200 h, and utilization-side units 120 which correspond to the HEX unit 101 h, the compressor unit 111 h, the valve unit 200 h, and the utilization-side units 120 according to the fifth embodiment, respectively.

The HEX unit 101 n includes an outdoor heat exchanger 102 n corresponding to the outdoor heat exchanger 102 h of the fifth embodiment, and the compressor unit 111 n includes a compressor 112 n corresponding to the compressor 112 h of the fifth embodiment. Yet, the compressor unit 111 n does not include the switching mechanism 113 h, but includes a heat medium-refrigerant heat exchanger 117 n. The HEX unit 101 n and the compressor unit 111 n are connected by a supply pipe 107 n and a return pipe 108 n (first connection pipes) such that the heat medium circulates therebetween. The HEX unit 101 n may be a closed type cooling tower which cools the heat medium flowing in the outdoor heat exchanger 102 n by supplying air while sprinkling water, but is not limited to this.

The heat medium-refrigerant heat exchanger 117 n is configured to allow each of the heat medium and the first refrigerant to flow therein so as to exchange heat between the heat medium and the first refrigerant. The heat medium-refrigerant heat exchanger 117 n is connected to the outdoor heat exchanger 102 n via the supply pipe 107 n and the return pipe 108 n. The air conditioning system 100 n further has a pump 118 n disposed to the supply pipe 107 n or the return pipe 108 n, preferably as part of the compressor unit 111 n. The pump 118 n is configured to induce a flow of the heat medium.

Hence, the outdoor heat exchanger 102 n, the pump 118 n, the heat medium-refrigerant heat exchanger 117 n, and the pipes connecting them form the first circuit 105 n which circulates the heat medium.

The heat medium-refrigerant heat exchanger 117 n is also connected to the discharge port of the compressor 112 m and the liquid refrigerant pipe 131 extending to the heatsource-side liquid pipe portion 310 of the valve unit 200 h. The suction port of the compressor 112 m is connected to the gas refrigerant pipe 132 extending to the low-pressure gas pipe portion 320.

Hence, the compressor 112 m, the heat medium-refrigerant heat exchanger 117 n, the indoor heat exchangers 122 m, and the pipes connecting them form the second circuit 106 n which circulates the first refrigerant.

The HEX unit 101 n is installed in the first space 931 h, the compressor unit 111 n and the valve unit 200 h are installed in the second space 932 h, and the utilization-side units 120 are installed in the target space 933 h. Any of the safety systems 700 h 700 i, 700 j, 700 k according to the first embodiment and its variations may be applied to the air conditioning system 100 n.

With the above configuration, it is possible to improve the safety of the air conditioning system of a water-cooling type regarding refrigerant leakage. The configuration of the sixth embodiment may be combined with the configuration of the fifth embodiment. In this case, the compressor unit 111 n further has the refrigerant heat exchanger 114 m and part of the refrigerant pipes 131 m, 132 m for the second refrigerant (and preferably the pump 116 m), and include a refrigerant circuit for circulating the first refrigerant between the compressor 112 h and the refrigerant heat exchanger 114 m.

(Other Modifications of Fifth to Seventh Embodiments)

In the above-mentioned fifth to seventh embodiments, the configurations are explained in which a forced ventilation of the second space 932 h is performed when a refrigerant leakage has been detected. Yet, a natural ventilation may be utilized instead of performing the forced ventilation.

FIG. 23 is a schematic configuration diagram of another variation of the safety system according to any one of the fifth to seventh embodiments.

As shown in FIG. 23 , a safety system 700 p as a variation may have the same configuration as the first embodiment except that the ventilator 730 is replaced with a damper 440. Both the dampers 440 disposed to the first and second airflow passages 935 h, 936 h are closed in normal times. The central controller 800 p corresponding to the central controller 800 h of the fifth embodiment and may have the same hardware configuration as the central controller 800 h. The central controller 800 p is configured to perform basically the same operation as the central controller 800 h. However, the central controller 800 p does not perform the operation of step S3030 h, and instead, control both the dampers 440 to open in step 3040 h.

In other words, the safety system 700 p has a passage control structure that is configured to, when the detected concentration of the first refrigerant is equal to or greater than the first detection value threshold, switch a state of the first and second airflow passages 935 h, 936 h from a normal state (a first passage state) to an emergency state (a second passage state) in which air is allowed to pass through the passages 935 h, 936 h more easily than in the normal state.

Thus, as with the safety systems already explained, the safety system 700 p can also switch the state of the second space from a first state to a second state in which a ventilation of the second space 932 h is promoted more than in the first state when the detected concentration of the first refrigerant is equal to or greater than a first detection value threshold. Although the ventilation achieved would be weaker than when a forced ventilation is performed, it is possible to reduce the cost of the safety system since a ventilator can be omitted.

Instead of the damper or dampers 440, any other mechanism which can switch the state of the first and/or second airflow passage 935 h, 936 h to the second state mentioned above may be used. For instance, a shutter, a window plate, or a door plate may be used. In any cases, the switch from the first state to the second state must be controllable from the central controller 800 m by means of an electric motor or the like.

In addition, other various modifications of the air conditioning systems explained above may also be conceivable. For instance, the compressor unit and the valve unit may be integrated to a single unit. In this case, the safety systems as shown in FIGS. 14, 18, 20, and 23 may be suitable.

As already mentioned above, the air conditioning system according to any of fifth to seventh embodiments may have the three-pipe configuration. The air conditioning system may include a plurality of the valve units as with the first to fourth embodiments, and, between the valve unit and the utilization-side units 120, one or more of the other valve units may be disposed. In particular when two or more of the valve units are installed in the second space together with the compressor unit, the casings of all of them may be connected by the connection structure.

The heatsource-side liquid pipe portion 310 and the gas pipe portion or portions 320, 340 need not necessarily be branched towards two or more of the utilization-side units 120 but directed towards only one among the utilization-side units 120. Yet, when the valve unit has at least a liquid refrigerant pipe portion, a gas refrigerant pipe portion, a liquid control valve disposed in the liquid refrigerant pipe portion, and a gas control valve disposed in the gas refrigerant pipe portion within the casing, the safety system can improve the safety regarding refrigerant leakage of the air conditioning system.

The first space, the second space, and the target space need not necessarily belong to the same building. Thus, for instance, the HEX unit may be installed on a ground outside a building, and/or the first space and the second space may be formed in different buildings. The term “building” includes a house, a hut, a ship, or the like.

The damper 440 may also be disposed to the first opening 420 to which the connecting duct 740 a is connected, as with the second embodiment as shown in FIG. 6 .

The number of the air passage, the number of the HEX unit connected to each compressor unit, the number of the compressor unit connected to each HEX unit, the number of the utilization-side unit connected to each compressor unit, the number of the utilization-side unit belonging to each unit family, and the number of the each of the first space, the second space, and the target space are not limited to those explained above. The utilization-side units belonging to the same valve unit may be installed different target spaces.

While only selected embodiments and modifications have been chosen to illustrate the present invention, it will be apparent to those skilled in the art from this disclosure that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, unless specifically stated otherwise, the size, shape, location, or orientation of the various components can be changed as needed and/or desired so long as the changes do not substantially affect their intended function. Unless specifically stated otherwise, components that are shown directly connected or contacting each other can have intermediate structures disposed between them so long as the changes do not substantially affect their intended function. The functions of one element can be performed by two, and vice versa unless specifically stated otherwise. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time. Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only.

REFERENCE SIGNS LIST

-   -   100, 100 h, 100 m, 100 n: Air Conditioning System     -   101 h, 101 m, 101 n: HEX Unit (Heat Exchanger Unit)     -   102 h, 102 m, 102 n: Outdoor Heat Exchanger     -   103 m: Unit Liquid Refrigerant Pipe (First Connection Pipe)     -   104 m: Unit Gas Refrigerant Pipe (First Connection Pipe)     -   105 m, 105 n: First Circuit     -   106 m, 106 m: Second Circuit     -   107 n: Supply Pipe (First Connection Pipe)     -   108 n: Return Pipe (First Connection Pipe)     -   110, 110 h, 110 m: Heatsource-Side Unit     -   111 h, 111 m, 111 n: Compressor Unit     -   112 h, 112 m: Compressor     -   113 h, 113 m: Switching Mechanism     -   114 m: Refrigerant Heat Exchanger     -   116 m, 118 n: Pump     -   117 n: Heat Medium-Refrigerant Heat Exchanger     -   120, 120 m: Utilization-Side Unit (Indoor Unit)     -   121, 121 m: Unit Family     -   122 h, 122 m: Indoor Heat Exchanger     -   131, 131 m: Liquid Refrigerant Pipe (Second Connection Pipe)     -   132, 132 m: Low-Pressure Gas Refrigerant Pipe (Second Connection         Pipe)     -   133: High-Pressure Gas Refrigerant Pipe     -   141: Heatsource-Side Liquid Pipe     -   142: Heatsource-Side Low-Pressure Gas Pipe     -   143: Heatsource-Side High-Pressure Gas Pipe     -   151, 151 m: Utilization-Side Liquid Refrigerant Pipe (Second         Connection Pipe)     -   152, 152 m: Utilization-Side Gas Refrigerant Pipe (Second         Connection Pipe)     -   200, 200 d, 200 h, 200 m: Valve Unit     -   300: Multi Branch Selector     -   310, 310 m: Heatsource-Side Liquid Pipe Portion     -   311, 311 m: Utilization-Side Liquid Pipe Portion (Liquid         Refrigerant Pipe Portion)     -   320, 320 m: Low-Pressure Gas Pipe Portion (Gas Refrigerant Pipe         Portion)     -   321: Low-Pressure Gas Sub Pipe (Gas Refrigerant Pipe Portion)     -   330, 330 m: Utilization-Side Gas Pipe Portion (Gas Refrigerant         Pipe Portion)     -   340: High-Pressure Gas Pipe Portion (Gas Refrigerant Pipe         Portion)     -   341: High-Pressure Gas Sub Pipe (Gas Refrigerant Pipe Portion)     -   351: Bypass Pipe     -   352: Refrigerant Heat Exchanger     -   361: Low-Pressure Gas Control Valve (Gas Control Valve)     -   362: High-Pressure Gas Control Valve (Gas Control Valve)     -   363: Expansion Mechanism     -   364, 364 m: Liquid Shut-Off Valve (Liquid Control Valve)     -   365, 365 m: Gas Shut-Off Valve (Gas Control Valve)     -   370: Pipe Connection Part     -   400: Casing     -   401: Internal Space     -   410: Pipe Aperture     -   420: First Opening     -   430: Second Opening     -   440: Damper (Check Air Damper, Ventilation Control Structure,         Passage Control Structure, Discharge Structure)     -   450: Insulator     -   500: Refrigerant Leakage Detector (First Leakage detector)     -   501 m: First Leakage Detector     -   502 m: Second Leakage Detector     -   600, 600 m: Unit Controller (Controller, Ventilation Control         Structure, Discharge Structure)     -   700, 700 a, 700 b, 700 c, 700 h, 700 i, 700 j, 700 k, 700 m, 700         p: Safety System     -   701 c: Section     -   710: Individual Ducts (Connection Structure)     -   720, 720 a, 720 b: Shared Duct (Discharge Structure, Ventilation         Control Structure)     -   730: Ventilator (Discharge Structure, Ventilation Control         Structure)     -   740 a: Connecting Duct (Connection Structure)     -   750 i: Intake Duct (Ventilation Control Structure)     -   800, 800 a, 800 b, 800 c, 800 h, 800 i, 800 m: Central         Controller (Controller, Ventilation Control Structure, Discharge         Structure)     -   801: Communication Path     -   910 b, 910 c: Grouping Table     -   931 h: First Space     -   932 h: Second Space     -   933 h: Target Space     -   934 h: Building Structure     -   935 h: First Airflow Passage     -   936 h: Second Airflow Passage     -   937 j: Third Airflow Passage

CITATION LIST Patent Literature

-   [PTL 1] EP 3 091 314 A 

1. An air conditioning system comprising: a compressor unit that has a compressor configured to compress first refrigerant; a heat exchanger unit that has an outdoor heat exchanger configured to exchange heat between air and the first refrigerant or between air and heat medium, the heat medium being subjected to a heat exchange with the first refrigerant; at least one indoor unit that has an indoor heat exchanger configured to exchange heat between the first refrigerant and air in a target space to be air-conditioned or between second refrigerant and air in the target space, the second refrigerant being subjected to a heat exchange with the first refrigerant; and at least one valve unit that has at least one liquid refrigerant pipe portion and at least one gas refrigerant pipe portion configured to allow the first refrigerant or the second refrigerant to flow therein between the compressor unit and the indoor unit, at least one liquid control valve disposed in the liquid refrigerant pipe portion, and at least one gas control valve disposed in the gas refrigerant pipe portion, wherein: the heat exchanger unit is installed in a first space; the compressor unit and the valve unit are installed in a second space which is different from any of the target space and the first space; and the air conditioning system further comprises a first leakage detector that is disposed in the second space and configured to detect at least a concentration of the first refrigerant in air, and a ventilation control structure that is configured to switch the state of the second space from a first state to a second state when the detected concentration of the first refrigerant is equal to or greater than a first detection value threshold, in the second state a ventilation of the second space being promoted more than in the first state.
 2. The air conditioning system according to claim 1, wherein the ventilation control structure includes a passage control structure that is configured to, when the detected concentration of the first refrigerant is equal to or greater than the first detection value threshold, switch a state of at least one airflow passage between the second space and an outer space outside of the second space from a first passage state to a second passage state, in the second passage state air being allowed to pass through the passage more easily than in the first passage state.
 3. The air conditioning system according to claim 1, wherein the ventilation control structure includes a discharge structure that is configured to operate to discharge air from the second space when the detected concentration of the first refrigerant is equal to or greater than the first detection value threshold.
 4. The air conditioning system according to claim 3, wherein the discharge structure includes a ventilator that is configured to draw air from the second space towards an external space which is different from any of the target space and the second space, a controller that is configured to control the ventilator to operate when the detected concentration of the first refrigerant is equal to or greater than the first detection value threshold, and a check air damper that is configured to keep closed an airflow passage between the second space and an outer space outside of the second space, and open the airflow passage when the ventilator is in operation.
 5. The air conditioning system according to claim 4, wherein: the second space is defined by a building structure; and the ventilator and the check air damper are disposed to the building structure.
 6. The air conditioning system according to claim 4, further comprising: first and second casings one of which accommodates the compressor unit and another one of which accommodates the valve unit as part of the second space; a connection structure connecting the internal spaces of the first and second casings; an intake duct connecting the outer space of the second space and the internal space of the first casing; and a discharge duct connecting the internal space of the second casing and the external space, wherein the first leakage detector is disposed in the first or second casing that accommodates the compressor, the check air damper is disposed to the intake duct, and the ventilator is disposed to the discharge duct.
 7. The air conditioning system according to claim 4, further comprising: first and second casings one of which accommodates the compressor unit and another one of which accommodates the valve unit as part of the second space; a first intake duct connecting the outer space of the second space and the internal space of the first casing; a second intake duct connecting the outer space of the second space and the internal space of the second casing; a connection structure connecting the internal spaces of the first and second casings; a discharge duct connecting the connection structure and the external space, wherein the first leakage detector is disposed in the first or second casing that accommodates the compressor, the check air damper is disposed to each of the first and second intake ducts, and the ventilator is disposed to the discharge duct.
 8. The air conditioning system according to claim 4, further comprising: a casing accommodating the compressor unit and the valve unit as part of the second space; an intake duct connecting the outer space of the second space and the internal space of the casing; a discharge duct connecting the internal space of the casing and the external space, wherein the first leakage detector is disposed in the casing, the check air damper is disposed to the intake duct, and the ventilator is disposed to the discharge duct.
 9. The air conditioning system according claim 4, wherein: the indoor heat exchanger is configured to exchange heat between the second refrigerant and air in the target space; the liquid refrigerant pipe portion and the gas refrigerant pipe portion of the valve unit are configured to allow the second refrigerant to flow therein; the air conditioning system further comprises a second leakage detector that is disposed in the second space and configured to detect at least a concentration of the second refrigerant in air; and the controller is further configured to control the ventilator to start operating when the detected concentration of the second refrigerant is equal to or greater than a second detection value threshold.
 10. The air conditioning system according to claim 9 which includes the first and second casings, wherein: the compressor unit further has a refrigerant heat exchanger configured to exchange heat between the first refrigerant and the second refrigerant; the first leakage detector is disposed in the first casing; and the second leakage detector is disposed in the second casing or a space which is part of the second space and not part of the internal spaces of the first and second casings.
 11. The air conditioning system according to claim 1, further comprising: first connection pipes connecting the outdoor heat exchanger unit and the compressor unit such that the first refrigerant or the heat medium circulates therebetween; and second connection pipes connecting the compressor unit, the valve unit, and the indoor unit such that the first refrigerant or the second refrigerant circulates between the compressor unit and the indoor unit via the valve unit.
 12. The air conditioning system according to claim 1, wherein: the air conditioning system comprises a plurality of the indoor units; and the valve unit further has at least one liquid refrigerant branch pipe branching the liquid refrigerant pipe portion towards the indoor units and at least one gas refrigerant branch pipe branching the gas refrigerant pipe portion towards the indoor units.
 13. The air conditioning system according to claim 1, wherein the second space is a space which is any one of a machine room, a computer room, and a warehouse in a building.
 14. A method for constructing the air conditioning system according to claim 1, comprising: installing the compressor unit and the valve unit in the second space which is defined by a building structure of a building; disposing the first leakage detector in the second space; installing the heat exchanger unit in the first space; installing the indoor unit in a space which is within the building and different from the first space and the second space; connecting the outdoor heat exchanger unit and the compressor unit such that the first refrigerant or the heat medium circulates therebetween; connecting the compressor unit, the valve unit, and the indoor unit such that the second refrigerant circulates between the compressor unit and the indoor unit via the valve unit; and installing the ventilation control structure to the building.
 15. The method for constructing the air conditioning system according to claim 14, wherein the building structure includes a floor, a ceiling facing the floor, at least one wall which connects the floor and the ceiling and surrounds a space between the floor and a ceiling, and a door arranged in the floor, the ceiling, or the wall.
 16. The air conditioning system according to claim 5, further comprising: first and second casings one of which accommodates the compressor unit and another one of which accommodates the valve unit as part of the second space; a connection structure connecting the internal spaces of the first and second casings; an intake duct connecting the outer space of the second space and the internal space of the first casing; and a discharge duct connecting the internal space of the second casing and the external space, wherein the first leakage detector is disposed in the first or second casing that accommodates the compressor, the check air damper is disposed to the intake duct, and the ventilator is disposed to the discharge duct.
 17. The air conditioning system according to claim 5, further comprising: first and second casings one of which accommodates the compressor unit and another one of which accommodates the valve unit as part of the second space; a first intake duct connecting the outer space of the second space and the internal space of the first casing; a second intake duct connecting the outer space of the second space and the internal space of the second casing; a connection structure connecting the internal spaces of the first and second casings; a discharge duct connecting the connection structure and the external space, wherein the first leakage detector is disposed in the first or second casing that accommodates the compressor, the check air damper is disposed to each of the first and second intake ducts, and the ventilator is disposed to the discharge duct.
 18. The air conditioning system according to claim 5, further comprising: a casing accommodating the compressor unit and the valve unit as part of the second space; an intake duct connecting the outer space of the second space and the internal space of the casing; a discharge duct connecting the internal space of the casing and the external space, wherein the first leakage detector is disposed in the casing, the check air damper is disposed to the intake duct, and the ventilator is disposed to the discharge duct.
 19. The air conditioning system according to claim 5, wherein: the indoor heat exchanger is configured to exchange heat between the second refrigerant and air in the target space; the liquid refrigerant pipe portion and the gas refrigerant pipe portion of the valve unit are configured to allow the second refrigerant to flow therein; the air conditioning system further comprises a second leakage detector that is disposed in the second space and configured to detect at least a concentration of the second refrigerant in air; and the controller is further configured to control the ventilator to start operating when the detected concentration of the second refrigerant is equal to or greater than a second detection value threshold.
 20. The air conditioning system according to claim 6, wherein: the indoor heat exchanger is configured to exchange heat between the second refrigerant and air in the target space; the liquid refrigerant pipe portion and the gas refrigerant pipe portion of the valve unit are configured to allow the second refrigerant to flow therein; the air conditioning system further comprises a second leakage detector that is disposed in the second space and configured to detect at least a concentration of the second refrigerant in air; and the controller is further configured to control the ventilator to start operating when the detected concentration of the second refrigerant is equal to or greater than a second detection value threshold. 